You select forward gear, the engine revs climb, but the boat barely moves. Or you hear a rattling from the engine bay that wasn’t there last season. Replacing a reverse gear costs between €350 and €1,950 for parts, but in many cases, the coupling itself isn’t the problem.
In this blog, you’ll read which symptoms belong to which type of gearbox, which three things you should rule out first, and what the costs precisely consist of. This way, you’ll know whether to order a new one or check something simpler first.
What does a reverse gear do on a boat?
You use it every time you moor, without giving it a second thought. A reverse gearbox is the transmission between your engine and the propeller shaft that reverses the direction of rotation, can stop the propeller, and reduces engine speed by a fixed ratio.
Many boat owners are unaware of this last function. The rating plate will show a ratio such as 2:1 or 2.47:1, and this figure determines how many times slower the propeller shaft rotates than the engine. When replacing it, this ratio must be correct, otherwise the gearbox will not match your propeller.
For diagnosis, the type is especially important:
- Mechanical reverse gear. The main shaft and auxiliary shaft are continuously connected via gears, reverse is via an extra gear. There is a small amount of oil in it which must be kept clean.
- Hydraulic reverse gear. A plate clutch is pressed by oil pressure, operated via pistons. Here the oil does the work, so oil pressure and oil level are critical.
The type you have determines what complaints you get with wear. That makes the distinction the quickest diagnostic tool you have.

Reverse gear problems: broken or is it something else?
You hear or feel something, but you don’t know if it’s serious. The symptoms of a worn reverse gear differ by type, and it’s precisely those differences that tell you where to look.
Symptoms of a mechanical gearbox
- Rattling from the engine bay. A rattling noise at idle or when engaging a gear indicates play in the gears or wear of the rotating parts.
- Judder from the gearbox itself. A high, constant tone that follows the engine speed usually comes from the bearing.
- Heavy or jerky gear changes. If the lever feels heavy, first check the cable, as this is a more common cause than the gearbox.
- Cannot engage. If forward or reverse has completely disappeared, something has broken internally and continuing to sail is pointless.
Symptoms of a hydraulic gearbox
- Slip. The engine speed rises, but the boat does not accelerate. With a hydraulic gearbox, this almost always means insufficient oil pressure or worn clutch plates.
- Fewer knots at the same engine speed. If last season you were achieving 6 knots at 1800 rpm and now it’s 5, then the clutch is slipping under load.
- Delayed engagement. A noticeable pause between lever and movement indicates oil pressure building up too slowly.
Why is my gearbox rattling?
Chattering and rattling often don’t come from the reverse gearbox itself. Between the flywheel and the reverser gearbox is the damper plate, a plate with springs or plastic pads that absorbs engine shocks. If these springs or pads wear out, the vibrations enter the drivetrain undamped, and you’ll hear this as rattling at low revs or a clatter when shifting.
Because the damper plate is attached to the reverser gearbox, the noise seems to come from there. If you recognise this pattern, first read how to replace your boat’s damper plate before considering a new gearbox.
Carry out these checks before ordering a new clutch
You’ve recognised the symptoms and are thinking about replacement. However, there are four points that are more often the cause than the reverser gearbox itself, and you can check them all in an hour.
- Oil level and oil type. A reverser gearbox that runs dry wears out quickly and overheats. Too much oil is just as bad, as it builds up pressure. Check which oil your model requires in the manual, as mechanical and hydraulic clutches don’t ask for the same thing.
- The condition of the oil. Does the oil smell burnt, or do you see metal particles on the dipstick? Metal particles mean something is already wearing down internally, and fresh oil won’t be a solution anymore.
- Cable, operation and adjustment. In many cases, stiff gear changes are due to a seized or incorrectly adjusted gear change cable, not the clutch. Feel if the lever moves without resistance when you disconnect the cable at the clutch.
- Engine mounts and alignment. Sagging engine mounts pull the drivetrain out of alignment, putting sideways stress on the gearbox bearings. Therefore, check the alignment of your propeller shaft as well.
There is another cause that is not a defect but a habit. Accelerating before engaging the clutch, or shifting directly into reverse from full speed, puts heavy strain on the plates and gears. Engaging the clutch first and then accelerating extends the lifespan of every gearbox.
If these points are satisfactory and the complaints persist, you’ll be looking at a rebuild or replacement.
Service or replacement: when do you choose which?
The size of your gearbox often determines half the answer. With a small, light gearbox, refurbishment is rarely worthwhile: dismantling, measuring, cleaning, and rebuilding it takes just as many hours as with a heavy gearbox, while a complete used or new unit is relatively inexpensive. The labour costs quickly exceed the price of a replacement gearbox.
Replacement is the logical choice in cases of internal damage, recurring faults, and when you need to get back on the water quickly mid-season.

How much does it cost to replace a reverse gear?
You want to know where you stand before you let someone take a look. The gearbox itself is the biggest item: used reverse gearboxes range from approximately €350 for a small mechanical Technodrive TMC40 to approximately €1,950 for a heavier ZF25 or a Kanzaki KM4a. The majority of the offerings are between €450 and €750.
What determines the price within that range:
- Type and format. A Hurth HBW50 for a 20 hp engine costs €450, a ZF25 for a considerably larger engine €1,950. Hydraulic gearboxes are structurally more expensive than mechanical ones.
- The ratio. The reduction must match your propeller. A 2:1 is readily available, a different ratio like 2.63:1 limits your choice and thus your price advantage.
- New or used. A new gearbox from Technodrive or PRM costs more than a used one from stock, but you get something back for it: a warranty, a known history, and parts that will remain available for years to come. If you sail a lot, the boat is your home or your work, or you simply want to have no worries for years to come, then new is the most peaceful choice.
In addition to the gearbox, these costs will be added:
- Removal and installation. The gearbox needs to be supported and sometimes the engine has to be lifted slightly. In a cramped engine room, this accounts for the majority of the labour time.
- Blanking plate. Include that straight away, because you’re there anyway and a worn plate will ruin your new gearbox.
- Oil and seals. Fresh oil of the correct type should be part of a replacement as standard.
- Alignment after reinstallation. The flanges must be realigned parallel; otherwise, you will immediately put new stress on the new coupling.
Order your parts from us, and we’ll ship for €6.95 within the Netherlands, and for free on orders over €125. New items come with a two-year warranty.
Do the job off-season if you can. In the spring, workshops are full, and you’ll be waiting longer than in november.
Which gearbox is right for your boat?
Replacing a gearbox starts with the nameplate and not the webshop: without make, type, and ratio, you cannot determine which gearbox fits. Browse the selection of used gearboxes, or send us this information and we’ll find it for you:
- Make, type and ratio of your current gearbox. They are on the nameplate on the housing.
- Make, type and power of your motor. This allows us to check if the coupling can handle the torque.
- The symptoms and when they occur. Slipping under load indicates something different to rattling at idle.
- What the oil reveals. Colour, smell, and any metal particles reveal a lot about the internal condition.
Call 0514-745007 or send a message via WhatsApp. With that information, we can tell at once if we have a suitable coupling in stock.





























