Author: abmarineservice

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Charging a Lithium battery with a dynamo: how to do it safely and responsibly

LiFePO4 Accu 12,8V/150Ah NG Main Image

When switching to lithium batteries for your boat or motorhome, one question is paramount: how do you safely charge them via the dynamo? At first glance, it seems straightforward. The engine is running, the dynamo is supplying power, and the battery is charging. In reality, it’s a bit more complicated.

Without a proper setup, it’s possible to damage the battery. The dynamo can also become overloaded. Especially for boat and camper owners who are replacing their old lead-acid batteries with lithium systems, we’ll explain the best way to approach this.


Why lithium batteries can’t just be connected to a dynamo

A lithium battery works a little differently from a traditional lead-acid battery. With a lead-acid battery, it accepts less current as it gets fuller, and the dynamo is gradually less heavily loaded. A lithium battery continues to draw a high charging current until it’s almost completely full. This means the dynamo has to run at maximum power for longer.

What’s more, lithium batteries need a precise charging voltage. While a bit of leeway is usually fine with a lead-acid battery, lithium ones will immediately cut out the Battery Management System (BMS) if the voltage strays too high or too low. Standard dynamos and regulators often struggle to control this effectively.

Should the engine speeds or temperatures fluctuate, the dynamo can overheat and the V-belt can slip. Consequently, the battery won’t charge properly. We’ll cover three dangers of directly connecting a lithium battery to a dynamo.

Dynamo overheating

If a dynamo keeps running at full power, it will get hot after a while. Especially when idling, as the dynamo gets very little cooling then. This can eventually cause damage to the bearings, windings and diodes. We’d rather avoid that, of course.

Overheating of the dynamo leads to a gradual process of reduced performance. The dynamo appears to still be working for a long time, but consistently supplies a little less voltage. Eventually, the dynamo will stop working. Proper regulation and protection prevent these problems.

Incorrect charging voltages

A lithium battery requires a stable charging voltage. For LiFePO4 batteries, the correct charging voltage is usually between 14.2 and 14.6 volts, depending on the make and BMS type. A standard dynamo with a built-in voltage regulator isn’t designed to stay within those tight margins. This can result in the lithium battery never reaching a full charge.

It may also be that the voltage rises too much at higher RPMs. If the voltage is too high, the BMS intervenes and interrupts the charging current. This can cause sudden voltage spikes in the vehicle’s electrical system and lead to damage to sensitive equipment or the starter battery. The correct charging profile and a specific voltage are therefore very important.

Dynamo or wiring overload

A lithium battery will keep drawing maximum current. This causes a standard dynamo to overload. Components such as the internal wiring, fuses, and connections aren’t designed for this. Eventually, the V-belt could even burn out.

Especially with boats that have older engines or motorhomes with thin cables running between the engine bay and the battery bank, this is a problem. Therefore, it’s important to have everything in order for the lifespan of your battery and other systems.

Two clever solutions: external charge controller or DC-DC battery charger

Ensuring the dynamo remains protected against overload and overheating can be achieved in two ways: with an external charge controller or with a DC-DC battery charger. We’ll happily explain more about these options for safely and responsibly charging your lithium battery.

Lithium batteries have a low internal resistance, allowing them to draw high currents when charging, especially in more modern vehicles with so-called ‘smart dynamos’. These are controlled by the onboard computer and don’t supply power constantly, meaning charging lithium batteries requires extra care. Therefore, it’s important to choose a suitable battery charger that performs well in different ambient temperatures and prevents the battery from being charged if it’s too cold or too hot.

Charging a lithium battery with an external charge controller

An external charge controller’s role is to replace or control the dynamo’s built-in voltage regulator. The system allows the dynamor to operate at full power, monitors voltage and temperature, and automatically adjusts the charging profile to suit the battery type. It adapts automatically to the conditions.

With an external charge controller like the Mastervolt Alpha Pro, the full output of the dynamo remains available and there’s no risk of overloading. It’s a sound solution, particularly for larger boats or systems with high energy demands.

Charging a lithium battery with a DC-DC charger

A DC-DC battery charger works a little differently. This charger is connected between the starter battery and the lithium battery. This way, the dynamo first charges the starter battery, after which the DC-DC charger controlledly passes current to the lithium battery. The charger determines how much current it allows through and keeps the charging voltage within safe limits. You can also set it with a maximum charging current to prevent overloading.

You can use multiple DC-DC battery chargers in parallel to get more power. This makes them ideal when working with multiple battery banks. They’re also a good choice if you have space and cabling limitations.

Which option suits your situation best?

Every installation is a bit different. When making the right choice when switching from a lead-acid battery to a lithium battery, it’s wise to take into account your current engine, dynamo, battery bank, and usage needs.

Choosing an external charge controller

We recommend opting for an external charge controller if you want to get the most out of your existing dynamo. This solution is particularly well-suited to larger boats with a high energy demand from a substantial battery bank.

Even if you sail for a long time and often, an external charge controller has a clear advantage. Because the dynamo can deliver its full power, it can simultaneously supply power to the battery and other systems without overload.

Choosing a DC-DC battery charger

If you’re after flexibility, for example if you’re working with multiple battery banks or different battery types, then we’d recommend a DC-DC battery charger. The charger can be set to regulate the charging current and voltage itself. This protects both the dynamo and the battery from varying engine speeds.

You’ll also need a DC-DC charger if you plan to add extra battery banks or expand the system later. This is because multiple chargers can be placed in parallel to increase charging capacity. For the DIY enthusiasts among us, this is therefore a sensible and flexible choice. You can also combine and expand different power sources with it. Overloading the dynamo is almost impossible with this setup.

Orion XS 12/12-50A DC-DC acculader Main Image

Charging via a smart dynamo from AB Marine Service

Connecting a lithium battery directly to a standard dynamo, that’s not a good idea. Opt for an external charge controller or a DC-DC battery charger to safely and responsibly charge your lithium battery with a dynamo.

Do you have any questions about your situation? Don’t hesitate to get in touch with us. We’ll be happy to help you make the right choice. That way, you can soon be back on the water without a care, thanks to a modern battery system.

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Breakdown on the water

pech-op-het-water

Failures in your engine, collision with a sandbank, a fuel leak… these and other issues cause major problems while sailing and are the nightmare for many a skipper. You can prepare as well as you can, but it is obviously difficult to arm yourself against the unexpected. Do you have quite a bit of technical knowledge and also the necessary tools with you? Heartwarming! But that does not mean you can actually face all issues.

Prevention is hard, cure is not! That’s why you would be very wise to join our partner Vaarzeker to take out a subscription, which ensures you always get the best assistance!

Even if you are not a member, these counsellors may be able to support you. They are just a phone call away from you! Call +31 85 3038253 if you could use some assistance right now. Please note that if you are not a member, you cannot take advantage of free help and there is a good chance you will have to wait longer. Members of Vaarzeker always have priority!

Safety above all

A breakdown is very annoying, but potentially even dangerous! Before calling in Vaarzeker or any other assistance service, it is vital that you are safe yourself first. Especially in case of a fire, leak or power failure. As long as your fellow sailors and you are not at risk, you can plug a leak, put out a fire or switch off the power. In doing so, never expose yourself or others to unnecessary danger, ensure your safety above everything else and call in experts whenever possible!

Subscriptions

As is the case with many services, you are also in a position to decide how much you pay and thus what exactly your options are. That is, you only get assistance with the most important and common problems when you choose the cheapest subscription. With standard or even complete assistance, that package is of course increasingly magnified so that you are carefree on the water! On top of that, the latter two subscriptions offer a 10% discount to boaters who choose to pay per year instead of per month. The three modules are:

Breakdown Assistance
This module includes:

  • Call-out charges
  • On-board assistance
  • Starting aid for battery problems
  • Throughout the Netherlands except home port

As long as you are ashore, you can count on the most comprehensive assistance from experienced mechanics thanks to Breakdown Assistance. They do their utmost to get you out on the water the same day. Do you also want technical support while on open water? Then read on quickly!

Assistance Standard
If a technical failure occurs while you are on small inland waterways, your vessel will be towed to a safe port. The Wadden Islands are excluded.

This module includes:

  • Call-out
  • Towing off
  • Telephone assistance for technical questions
  • Telephone nautical advice

For a small extra fee, the Breakdown Assistance module is included in this. It is then offered at a 10% discount. Moreover, Assistance Standard is offered throughout the Netherlands, including your home port.

Assistance Complete
Whatever water you find yourself on, you will benefit from a comprehensive assistance package

This module includes:

  • Call-out
  • Towing off
  • Telephone assistance for technical questions
  • Telephone nautical advice
  • Floating after jamming
  • Supply of spare parts
  • Fuel delivery
  • Towing from port to port
  • Removal of objects from propeller

As with Assistance Standard, you can add Breakdown Assistance to this package: in this case, you get a discount of up to 15% on it! Assistance Complete can be used throughout the Netherlands, including your home port.

Carefree boating

When you go out on the water for fun, you always want to be able to count on experts to help you. Got a problem on board? Then you know who you can count on! After making just one phone call, Vaarzeker’s professionals will come to you to solve your problem. Depending on the situation, you can simply sail on to your final destination the same day. Give yourself that peace of mind, become a member and sail for sure.

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Water-lubricated propeller shaft leaks

boatymacboatface

To function, your ship’s propeller shaft runs from inside to outside, through the hull. Of course, this component is built and installed so that your vessel does not fill up with water, but still, your water-lubricated propeller shaft may leak. Naturally, this is a dangerous situation that you want to prevent or remedy as soon as possible. But how does this arise and how do you fix such a problem? Read on to find out why your water-lubricated propeller shaft is leaking and what to do about it.

Water-lubricated propeller shaft leaks: the cause

There is a difference between a grease-lubricated and a water-lubricated propeller shaft seal. Variants from the first category are easy and low-cost to maintain, but grease replacement is difficult. Moreover, some of this ends up in surface water, which is not environmentally friendly.

A grease-lubricated propeller shaft seal is easily converted to a water-lubricated one. You don’t have to constantly lubricate the grease pot and it is much less polluting anyway. But sand grains are capable of causing considerable wear to the sealing rings. And that, in turn, is the basis for a leak!

Furthermore, your engine may be set up a little too flexibly, meaning the packing rings are not sufficiently able to follow the propeller shaft movements. In addition, a leak may be due to stuffing boxes that seal radially and do not adjust to propeller shaft misalignment. Finally, it is possible that the axle itself may wear out and thus let in water.

Water-lubricated propeller shaft leaks: the solution

The bearings of a water-lubricated propeller shaft installation are made of rubber. These may need to be replaced once in a while to prevent or fix leaks, if you already suffer from leaks.

Do you often sail in waters known to be shallow or sandy for other reasons? Then it’s better to switch to a grease-lubricated propeller shaft. Indeed, as we explained above, that sand is going to affect your seal much faster than you would like. You are much less likely to suffer from that with a grease-lubricated system. The downside is that this requires much more maintenance. That is much less the case with a water-lubricated propeller shaft. But periodically checking that all components are still in full working order can never hurt.

Questions?

That comes in handy, because we have answers! Now if you have a problem with your water-lubricated propeller shaft that is not mentioned here, feel free to contact us . Explain the problem to us so that we can provide you with a suitable solution. Besides just a method, we also have the best parts for you, such as a complete propeller shaft seal, a coupling and a grease cord.. You can easily install these yourself. At AB Marine Service, you can only assume the very highest quality, because we do offer it!

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How to connect a boat alternator

Does the warning light on the dashboard stay lit, or does the battery lack the oomph to start the engine after a while? Time to replace your boat engine’s alternator.

Follow these 3 steps to replace an alternator yourself

  1. Removing the alternator
  2. Buying the correct alternator
  3. Installing the new alternator

Or go directly to:

With conventional dynamos and alternators, one thick cable runs directly from the battery’s positive (Terminal B+) or to the distribution point on the starter motor. 

Turning on the dynamo usually happens via a warning light that visually indicates on the dashboard whether the circuit is complete. As soon as you turn on the ignition, this light will illuminate until the dynamo provides a counter-voltage while running. Does it not illuminate? Then also check the supply to the ignition L, or D+ on the dynamo. You can also simply connect this directly to the earth and see if it then illuminates. 

There are also dynamos that are “mass-free”. This means the entire system is isolated from earth (often the engine block). In this case, these cables must also be disconnected.

The AC signal from the dynamo is often used to drive the rev counter. This is frequently marked on the dynamo as the W terminal. If your rev counter isn’t working either, this is another indication that something is wrong. 

Removing the dynamo


Turn off the electrical system, disconnect the battery or main switch, and check that the voltage is actually off the cables and the charging cable runs to the battery (B+) or distribution point. Disconnect the dynamo’s electrical wires. Mark the disconnected wires so you know where they need to go back later. The dynamo is now free from the electrical system. You can detach it from the engine. Generally, it is attached to the front of the engine with a tensioner and mounting bracket. Sometimes accessibility isn’t ideal, especially in a cramped engine bay, but with some creative socket wrench and extension bar work, you’ll get there. Slacken the V-belt by releasing the tensioner (1&2). Remove the mounting bolt (3).

Dynamo vrij maken van motor
Close-up photo of an alternator

Buying the right alternator for your boat

On our website, you can easily search for the right alternator. The easiest way to find the right dynamo for your boat is by its number. This is often found on the casing with a sticker and/or engraving.

You can also find under the category alternator You can also find it under the category brand and type of the marine engine, or enter the engine type in the search bar. For each starter motor, you will see the dimensions and specifications. The most important measurements are in any case dimensions J1 and J2 (in the drawings C and A) and of course the entire execution of the suspension.

At AB Marine service, you can buy a (replacement) alternator for your specific brand. We have a category page for each brand. Including:

  • Volvo Penta alternator
  • Bosch
  • Delco Remy
  • Denso
  • Duccelier
  • Femsa
  • Hitachi
  • Iskra
  • Lucas
  • Magnetti Marelli
  • Magneton
  • Mande melroe
  • Mitsubishi Motorolla
  • Paris Rhone
  • SEV
  • Valeo
  • Visteon
  • OEM

Also watch our video: How to find the right dynamo for your boat?

Installing the new alternator

Installing the new alternator is the reverse of the steps described above. Ensure all surfaces are clean and free from corrosion. And note that grease is not conductive. Therefore, you should always grease the material after installation. This acts as a protective layer against moisture ingress. For proper protection between the contacts, use contact spray or conductive paste.

Alternator: codes and facts

Installing a dynamo is not complicated if you know what the codes mean. We are in all cases talking about alternators.

L or D+ contact: warning light on the dashboard

In most cases, a ship’s or boat’s alternator functions quite simply. A warning light on the dashboard illuminates when you turn the ignition key. When the engine is running, this light goes out. If the alternator is malfunctioning, you’ll sometimes see the light glowing dimly. This means the alternator has a low output and isn’t providing enough counter-voltage, causing current to flow slowly and the warning light to remain (dimly) illuminated. If the warning light isn’t working, the alternator won’t start either. This connection is often labelled L (lampje/light) or D+ (Dynamo+).

IG or R contact: always voltage for alternator

IG or R Contact is a switched wire from the ignition switch. The wire directly supplies the dynamo regulator with voltage, ensuring it always has voltage to engage.

Eenvoudige L en IG aansluiting met T-stekker
Schematic diagram Simple L and IG connection with T-connector

B+/ A or 30: Output voltage

An output voltage and current from the dynamo go to the battery. Sometimes a diode separator is fitted in between to charge two battery packs separately. You then split the current into two parts, as it were. We usually recommend the use of a battery isolator switch, because it draws less voltage from the charging voltage.

This outgoing voltage wire is often thicker than the others and is generally red. It is designated B+, A, or 30.

Minus sign and G: earth connection

Everything marked with a minus sign or G for Ground means an earth connection and can be connected to the engine or the negative terminal.

W: Tachometer for boat engine

If you have to deal with the tachometer, that is to say the rev counter. The alternator generates alternating current. Each of the coils (usually 3) produces a Hertz signal that increases with the engine speed. The rev counter can convert this signal into an engine speed indicated on the tachometer.

Alternator codes: connection codes per brand

All connection codes per make are shown in the image below. American dynamo models often have a very different coding from Japanese and German variants. However, at their core, the most important and common connections like B+ battery/ D+ lamp and W tachometer are often still present.

dynamo connection code table


Further information about the electrical circuit and testing the installation.

While sailing, the battery is charged by the alternator on the ship or boat’s engine. A battery supplies 12 or 24 volts. If you want more power on board, opt for a larger alternator that supplies more current. In most cases, we can supply an alternator with the same dimensions. Contact us, send us your current setup and as many numbers and details as possible, and we’ll find the right dynamo for you.

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How to replace your boat’s fuel filter

Replacing your boat’s fuel filter is a crucial part of maintaining your diesel engine. This filter prevents impurities, such as dirt and water, from reaching the engine via the fuel. Without a properly functioning fuel filter, you risk starting problems, reduced engine performance, and even serious engine damage.

In this blog, we’ll explain step-by-step how to install a new fuel filter, what tools you’ll need, and how to avoid mistakes. Whether you’re an experienced DIYer or just starting out, this guide will help you get started.

What you’ll need to replace a fuel filter

A good preparation is half the battle. Before you start replacing the fuel filter, make sure you have all the necessary materials and tools to hand. This will not only prevent delays but also minimise the risk of mistakes.

General supplies

For each type of filter, you’ll need the following items.

  • Cloths or absorbent material: Essential for soaking up spilled fuel and keeping your workspace clean.
  • A collection tray: For catching contaminated fuel and any lea.
  • A new fuel filter: Make sure you choose the correct model that fits your engine. Consult the engine’s manual or seek advice from our specialists.
  • Tools: Think screwdrivers, spanners, and filter pliers. These are needed for loosening and tightening the filter.

Specific requirements per filter type

  • Screw-on filters: A filter wrench to unscrew the old filter. If necessary, a rubber sealing ring to ensure a perfect seal.
  • Cassette types: Additional sealing rings. These are often supplied with the new filter, but always check that they are present.
  • Separ filters: A Separ filter is designed to separate water and dirt from fuel and contains a water-repellent filter element. It is important to check whether the filter element is reusable and if specific cleaning agents are required. Additionally, it is advisable to have a spare filter element to hand in case the old filter is full and no longer usable.

Step-by-step guide to replacing a fuel filter

Replacing a fuel filter might seem complicated, but with this structured approach, it’s a job you can do yourself. Below you’ll find a detailed guide per filter type.

Preparation

  1. Turn off the engine: Switch off the engine and wait for it to cool down completely. This prevents fire hazards and minimises the risk of burns.
  2. Work in a well-ventilated area: Fuel vapours can be harmful and flammable.
  3. Turn off the fuel supply: Close the fuel shut-off tap to prevent fuel from continuing to flow through the system during replacement. Check for any leakage at the valve, especially with older fuel lines.
  4. Place a drip tray: Place an oil and fuel-resistant drip tray under the filter to catch any leaking fuel. Use a rag to mop up any small spills immediately.

Replace screw-on filter

  1. Unscrew the old filter: Use a filter wrench to carefully unscrew the filter. Be careful to remove the rubber seal if it has been left behind on the engine, as a seal left behind can cause leaks.
  2. Check the new seal: Smear a thin layer of diesel oil onto the seal. This will ensure a better seal and prevent the filter from being overtightened.
  3. Fill the new filter with clean diesel: If your engine has a mechanical fuel pump, fill the new screw-on filter with clean diesel first. This will prevent air bubbles in the fuel system. (Note: with modern engines that have an electric pump, this is not necessary. With these, it can actually have the opposite effect and send dirt to the injectors. The engine’s manual is the definitive guide for this step.)
  4. Fit the new filter: Screw the filter on by hand until it sits snugly, then tighten it a further quarter turn. Do not use a filter wrench to tighten the new filter, as this can damage the seal.

Cassette types replace

  1. Remove the housing: Use the correct tool (usually a spanner or screwdriver) to carefully unscrew the filter housing and remove the old filter element.
  2. Clean the housing: Use a lint-free cloth to clean the inside of the housing. Avoid harsh cleaning agents as they can damage seals. Check for and remove any old seal rings left inside the housing.
  3. Install the new filter: Install the new cassette filter ensuring the sealing ring is correctly positioned and not twisted. Screw the housing on firmly, but do not overtighten to avoid damaging the seals.

Replacing or cleaning the separator filter

  1. Remove the filter element: Remove the filter element and dispose of the filter and old fuel.
  2. Fill the housing: Fill the filter housing with clean fuel and refit the filter. After refitting, check for fuel leaks at the connections.

Bleeding the fuel system

After replacing the fuel filter, you need to bleed the fuel system to prevent air in the lines from causing engine malfunctions or starting problems. Not all engines have manual bleeding, so check your engine’s manual for the correct procedure.

  1. Check if bleeding is necessary: Some modern engines with an electric fuel pump bleed automatically as soon as you turn the ignition on. Older or mechanical fuel systems need to be bled manually.
  2. Open the bleed screw: Undo the screw slightly until you see fuel emerging.
  3. Manually pump the fuel pump: Keep pumping until there are no more air bubbles in the fuel.
  4. Close the screw: Tighten the screw firmly, but not excessively to avoid damage, and start the engine to check that it runs smoothly.

Common mistakes and how to avoid them

Replacing the filter yourself can be a challenge, especially if you’re unfamiliar with the procedure. Here are some common mistakes and tips to avoid them.

Using the wrong filter

A new fuel filter must always be compatible with your engine. Using an unsuitable filter can lead to leaks or insufficient filtration. Always check the specifications and use an original or manufacturer-recommended filter.

Bleeding the system incorrectly

Air in the fuel system can have serious consequences, such as starting problems or a poorly functioning engine. Ensure you always bleed the system after replacement.

Reusing old seals

When replacing a filter, it is important to also replace the sealing rings. A damaged ring can lead to fuel leakage, which is not only inefficient but also dangerous. Always use a new sealing ring and check that the old ring has not been left behind on the engine.

Tightening the filter too much or not enough

A common mistake is overtightening the filter, which can damage the sealing ring. Conversely, a loose filter can cause leaks. Tighten the filter by hand until it seats properly, then give it an additional quarter turn. Do not use tools to tighten the filter unless specified by the manufacturer.

No preventative maintenance

Ignoring a clogged fuel filter can lead to severe engine damage. Regularly carry out preventative maintenance to extend your engine’s lifespan. Therefore, cleaning your fuel filter is a worthwhile endeavour.

Why a well-functioning fuel filter is important

A fuel filter plays a key role in ensuring your engine runs smoothly. It prevents unwanted particles, like dirt, rust, and water, from entering the fuel and subsequently the engine. If this happens, it can not only reduce engine performance but also lead to serious damage.

Protection against serious damage

When the filter loses its capacity to trap impurities, they can still enter the engine. This can damage the injectors or even lead to damage to the fuel pump. Injectors are highly precise components that are extremely sensitive to dirt and water. A damaged injector requires costly repairs or replacement.

Optimal fuel consumption

When a clogged fuel filter causes reduced flow, the engine has to work harder to draw in fuel. This not only leads to higher costs due to increased fuel consumption but can also result in reduced engine performance, such as a decrease in power and speed.

Longer engine life

A clogged fuel filter can have serious long-term consequences for your engine’s lifespan. If dirt and water enter the engine, they can cause corrosion in the fuel lines and vital components, such as the injectors and fuel pump. Furthermore, these impurities can cause the engine to overheat more quickly or even seize up completely.

How to recognise a clogged fuel filter?

It’s important to know when a fuel filter is getting clogged so you can intervene in good time. Here are some common symptoms:

  • Starting problems: A blocked filter can impede the fuel supply, making it difficult to get the engine going.
  • Reduced engine performance: If you notice the engine is losing power or running unevenly, a blocked filter could be the culprit.
  • Increased fuel consumption: An inefficient fuel system due to a blocked filter causes the engine to use more fuel than usual.
  • Rough idling: When the engine doesn’t run smoothly at idle, it can indicate a blockage in the filter system.
  • Smoke from the exhaust: Excessive or dark smoke can be a sign that the engine is struggling to combust fuel properly due to a lack of clean fuel.
  • Warning light: On some modern engines, a dashboard warning light may indicate that the filter is full and needs replacing.

If you notice one or more of these symptoms, it’s advisable to check the filter straight away and likely replace the fuel filter as a precaution. Want to know how to test when your fuel filter needs replacing? Then read our other blog where we explain when to change a fuel filter.

Replace the boat’s fuel filter yourself

Replacing the fuel filter is a relatively simple job that is important for maintaining the performance and lifespan of your engine. With the right preparation, the correct tools and this comprehensive guide, you can carry out this job yourself.

Do you have any questions or are you unsure which filter you need? Get in touch with our experts. They’ll be happy to help you!

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When should I change the fuel filter of my diesel engine?

When there is water, diesel bacteria (sludge) or dirt (under) in or on the fuel tank, it is time to replace the boat’s engine fuel filter.

Therefore, check the filters of the fuel system regularly. E.g. annually when preparing the boat for winter. Do you see water or dirt in the inspection hole of the filter? Then it is likely that there is also water, diesel bacteria (sludge) or dirt at the bottom of the fuel tank. In that case, replace the diesel fuel filter.

Also read: Slime strings and clogged fuel filters

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How to test and replace glow plugs in the diesel engine of my ship or boat

What are glow plugs?

A marine diesel engine has electric glow plugs that help it start when cold. Diesel engines use spontaneous combustion by compressing oxygen and fuel. Just before the highest pressure is reached and the piston is in the top position, fuel is injected through a vaporiser and the combustion process begins. As the engine can be very cold after not running for a while, it may need a little help. That is where the glow plugs come in. Glow plugs are located in the combustion chamber of the engine and are made of high-grade materials.

Testing a glow plug

To test the glow plug, measure the resistance using a multifunction meter or ohmmeter The wires are to be disconnected before measuring. The exact value of each plug varies, but a defective plug can easily be distinguished from a working one. If a current passes through and the ohmmeter shows a value, it would be fair to assume that the plug is in working order. If it reads infinite, there is an interruption and it would be fair to assume that the plug is defective.

Two types of glow plugs

Glow plugs come in two different types:

  1. Parallel glow plugs

    Parallel glow plugs are connected to earth (engine block) via the entry. The current flows back to the battery via the screw thread. They have one entry and are connected to one another. These are usually the Quick Glow Systems that run on the direct battery voltage.

  2. Serial glow plugs

    Serial glow plugs are working like a light bulb. These are often seen in old systems or spiral filaments. They have an incoming and outgoing wire or connection to the next one. The first plug is the entry and the last one is connected to earth. They work on reduced voltage with pre-heating resistors and a glow eye.

DIY replacement of glow plugs on a marine engine.

Remove any defective glow plugs. NB: they can be very tight, so be very careful, especially when dealing with thin-walled glow plugs. Spray generously with penetrating oil before removal if corrosion has built up around the plugs. Thicker plugs are less particular because of their different diameter and plug ratio.
Keep the area around the opening of the motor clean. Watch the maximum loosening torques (Nm = Newton metre = unit of torque) and the thread size (M).

Tip: also use a torque spanner for loosening.

Maximum loosening torques

  • M8 – 20 Nm
  • M9 – 22 Nm
  • M10 – 35 Nm
  • M12 – 45 Nm

Fitting new glow plugs

When fitting new glow plugs, it would be best to use the tightening moment as prescribed by the engine manufacturer. A little copper grease on the cutting edge and the thread is recommended. Tightening is also done with a tightening moment. They only need to seal. Indication of tightening moments for electrical connections:

  • M8 – 10 Nm
  • M9 – 12 Nm
  • M10 – 15 Nm
  • M12 – 22 Nm

Tightening moment for electrical connections

  • M4 – 2 Nm
  • M5 – 3 Nm

Removal of jammed glow plugs

When the maximum removal torque has been reached, discontinue the loosening effort and do not overstrain. That is because the glow plug may break. And that means dismantling the entire cylinder head. Try to loosen the glow plugs in the following three steps:

  1. Loosening: Spray with penetrating or synthetic oil. Repeat several times during the day and leave it to soak in overnight.
  2. Heat the plug: Expanding and contracting materials may create more play. Tune up the engine or use a power cable to warm up the self-regulating glow plugs and proceed a little longer than usual. Repeat this procedure. Please note: This procedure works only on glow plugs with 11 – 12V operating voltage.
  3. Loosening: Try to unscrew the glow plug once again. Using a suitable tool, carefully unscrew the glow plug in the cylinder head. A long, extended socket wrench often works better than a spanner. This will distribute the force more evenly without the need for straining it sideways. Use a tap wrench to work with both hands. If no luck, repeat the above three steps.
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How to install an inboard engine?

Are you planning to install or modify an inboard engine yourself? Prepare well, start with the basics, and take measurements. With minimal adjustments, you can replace an engine. For recent engines, you often know the installation dimensions or they are easy to find. Pay special attention to:

Make sure to figure out what you need.

Are you still looking for a used engine? Quickly check out our range of used marine engines.

Propeller shaft height

First, check if the engine fits in combination with the propeller shaft height. Is the output of the reverse coupling at the same height as the crankshaft? If the output of the reverse coupling is lower than the existing propeller shaft, the engine will need to be raised.

Engine mounts

On some inboard engines, adjusting the existing engine mounting points is no problem, or the foundation of the steel hull can be modified. In a polyester boat, this becomes more difficult. Therefore, check beforehand if this is possible. Especially with a saildrive, you’re often bound to existing prefab transom fittings.

Maximum tilt

Also check if the inboard engine can handle the maximum tilt while sailing. The maximum tilt is often listed in the manual. A homokinetic drive solves the problem otherwise.


Reverse coupling

The Velvet, PRM reverse coupling, Hurth, ZF, and Twindisc reverse couplings are common reversing couplings. The ratio is often indicated by the engine RPM divided by the output RPM, in a two-to-one (2:1) ratio. Ratio = Two engine revolutions / one propeller shaft revolution (or simply half).

The rotation direction of the output is often indicated as L or R in the 2:1 ratio. L is a two-to-one left-turning reverse coupling for a left-handed propeller.

You may also encounter reverse couplings with an A for angle, for example, in Volvo Penta. These reverse couplings come with a shaft tilted 7 degrees outward. This way, the engine needs to tilt less.

Propeller

Pay attention to the rotation direction of the propeller. There are left-handed and right-handed reverse couplings. The rotation direction of the reverse coupling is indicated when the boat is moving forward and you are looking at the bow.

Be careful with a “Z-drive.” The engine is then reversed, so make sure to check the specifications carefully.

AB Marine Service can perform the power requirement calculation for your boat.

Power

If the power remains in the same direction, you can often reuse the same inlet and outlet connections, such as the exhaust gas outlet, cold water supply, or circulation pipes.

If you are increasing or decreasing the power, check the diameter of the connection on the engine. This is already a good indicator of the required size.

If the exhaust manifold is 45.00 mm, you can use this diameter. Do not go smaller, as it will restrict the engine, leading to potential issues. Going larger is usually not a problem.

Propeller shaft and bearing

Also think about connecting the propeller to the reverse coupling. Some brands are interchangeable, but this is not always the case. You will need an adapter flange. These can be obtained separately upon request or are often supplied ready-made with a homokinetic drive.

If you want to reduce vibration and save time with the connection, consider the advantage of a thrust bearing with a homokinetic drive.

What do you need?

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I have a 12V battery, but the alternator says 14V. What is the difference?

In boats, you have got 6V systems (old, but still common), 12V and 24V systems. The 12V is most common in pleasure cruising and 24V is found in larger ships and inland vessels.

This voltage is energised by the battery, which is recharged by an alternator on the combustion engine. This voltage is higher in order to fill ‘the vessel’ quickly. Without a voltage difference there is no ‘flow’. This creates the confusion between the terms system voltage and charging voltage.

There are also different batteries: starter, traction and semi-traction, sometimes with their own charging value. Real full-traction batteries require a higher charging voltage, always check this when purchasing.

On the AB Marine service site, we use the term ‘system voltage’ as much as possible. A 12V battery must be charged with a 12V alternator. Therefore we use the indication 12V for the alternator. Using the 14V or 13.8V charging voltage as indication would lead to confusion. We supply the alternators standard with a set value for charging starter and semi-traction batteries.

  • 6V calcium battery = 6.9V charging voltage (e.g. vintage car)
  • 12V calcium battery = 13.8V – 14.4V charge voltage (all starter batteries and common semi-traction batteries).
  • AGM semi-traction battery = 14.6V – 14.8V charging voltage
  • GEL battery = 14.2V – 14.8V charging voltage

It is also possible to determine the status of your battery by measuring the voltage, see the corresponding voltages below. Preferably do this a day after charging.

Gebruiksaanw. / Handleiding - Accu Service Holland

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Is your expansion vessel or cooling system running empty?

Is the expansion vessel or cooling system (slowly) losing pressure? It could be a leak in either direction.

First make sure that there is no leak to the outside of the engine. Leaking cooling liquid can evaporate quickly when the engine is hot, which makes it hard to detect. Look for traces of dried cooling liquid. This has usually the colour of the liquid itself: yellow, green or red, depending on the brand and type of liquid. It can easily be fixed by tightening the hose clamp or replacing a cooling water hose.

Sometimes, the leak may show up when using a pressure tester to apply pressure on the system. Also check that the rubber seal of the radiator cap (or expansion cap) is still intact and not worn out.

What if no traces of leaking cooling liquid can be seen?

If the liquid does not run out, it may also escape via the heat exchanger that is connected to the water from outside the vessel. It means that – the other way round – water from outside the vessel enters the cooling system.

As a test, pinch off the outgoing cooling hose from the water from outside the vessel at the exhaust injection elbow. With the engine running, the impeller pump should be building up pressure (no risk of damage) and the cooling system should start filling in case of a leak between the outside water system and the engine heat exchanger. The fluid level in the expansion vessel should rise. That is when it is time to replace the rubber sleeves. The sleeves separate the ”outside water system” from the ”coolant system”.

If all the above is not the case and the motor oil contains no cooling liquid, the engine may also have let cooling liquid enter into the combustion chamber. The cause could be a leaking head gasket or cracks in the cylinder head. Many mechanics cannot determine this fault from the outside for sure. Especially in case of a small leak, this is very unpleasant and hard to assess.

Possible solutions include:

A simple pressure tester (also useful for the first and second step). A low-cost solution, but make sure that the kit comes with the right cap. The tester is also available from AB Marine service, if so required. Alternatively, a nitrogen tester is also a reliable testing tool. It shows when nitrogen from the combustion gets into the cooling liquid. For this, google on e.g. “cylinder head leakage tester kit”.

If you cannot find the cause in steps one and two, remove the cylinder head for further inspection.

Spare parts for the cooling system