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Boat outdrive units - Reliable marine propulsion systems

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Boat outdrive units - Reliable marine propulsion systems

Improve your boat's propulsion with durable, compatible outdrives

What is a boat lower unit and what is its role?

The lower unit is the sealed submerged housing containing the reduction and gear-shifting system. On inboard engines (Sterndrive), it is referred to as a “Z” drive or Z-drive passing through the transom. On an outboard engine, the architecture is vertical and integrated into the engine leg.

Its mechanical role is threefold: transmitting the rotational movement from the vertical driveshaft to the horizontal propeller shaft through a set of bevel gears; allowing gear shifting (Forward / Neutral / Reverse) through a sliding clutch dog; and finally, drawing in raw water through intake grilles to cool the engine block via the water pump housed inside it.

The orientation of this lower unit, controlled by the steering and adjusted in angle by external hydraulic trim rams, makes it possible to steer the boat and adjust its trim while underway for clean planing.

How to choose the right boat lower unit

Choosing a replacement engine lower unit requires precision: it is not a simple accessory, but the drivetrain that absorbs all the engine torque. At DAM Marine, we help you identify the equipment strictly compliant with the original specifications of your engine, in order to ensure reliable propulsion at sea.

Technical criteria: power, shaft and rotation

Replacing a lower unit leaves no room for approximation. Three fundamental technical parameters must be checked on your engine identification plate:

The gear ratio: The internal gear reduction varies depending on engine power, propeller and the torque of your engine block. A V6 engine will not use the same ratio (e.g. 1.47:1) as a 4-cylinder inline engine, in order to optimize engine rpm in relation to thrust in the water.
The driveshaft length: It is essential to measure the engine shaft (short, long, extra-long or ultra-long) so that it matches the height of your transom. An incorrect shaft length will prevent any coupling with the engine block or cause severe cavitation problems on your outboard engines.
The direction of rotation and the number of splines: The propeller shaft rotates in standard rotation (right-hand - RH) or counter-rotation (left-hand - LH). This criterion is vital, especially on twin-engine installations where the flows must cancel each other out. In addition, the exact count of splines on the vertical driveshaft is essential to ensure proper engagement in the crankshaft.

Compatibility with major engine brands

There is no such thing as a universal lower unit. Each lower unit has its own casting specifications, mounting center distance and cooling circuit. Attempting to fit a non-compatible model is bound to result in mechanical failure. The goal is to replace your equipment with parts that are strictly equivalent to manufacturer dimensions. DAM Marine distributes replacement solutions perfectly calibrated for the leaders of the marine market. Whether you are looking for a Mercruiser lower unit (Alpha One, Bravo) for your Mercruiser Z-drive installations, a lower unit for a Honda outboard, or a pump body and housing for a Yamaha engine block, checking by engine serial number remains the only foolproof method. Browse our dedicated catalogs to identify your reference.

Signs of a worn or damaged lower unit

Wear on an engine lower unit is reflected in clear mechanical symptoms. A sharp metallic clunk when engaging forward or reverse gear often indicates pronounced wear of the clutch dog or an incorrect adjustment of the shift cable. A whistling sound while underway may indicate excessive play in the bearings or incorrect gear alignment.

The most critical symptom remains water intrusion into the lower unit housing. If, during draining, the oil has a milky appearance (commonly called “mayonnaise”), this confirms a sealing failure. The oil seals (lip seals) on the propeller shaft, driveshaft or shift rod are compromised. This defect directly endangers the bearings and gears of your lower unit due to lack of lubrication.

Following severe grounding (impact on a shoal), a bent propeller shaft or a cracked aluminum housing often makes reconditioning economically or technically unsuitable for ensuring onboard safety. Installing a new or reconditioned Mercury lower unit from Mercury becomes the most reliable solution for getting back to sea with confidence.

Maintaining your lower unit: oil change and prevention

The longevity of your transmission relies on rigorous preventive maintenance. The essential operation is changing the lower unit oil (marine gear oil, often SAE 90 or High Performance grade), to be carried out every 100 hours or during annual winterization. Inspecting magnetic drain plugs is crucial: the presence of fine grey metal dust is normal (running-in wear), but the presence of metal chips indicates internal gear failure in your lower unit.

Sealing cannot be checked with the naked eye. In case of doubt, or every three years on average, a mechanic will carry out a pressure and vacuum test on the housing. If the test fails, replacing the lower unit seal kit (oil seals, O-rings) is necessary before launching the boat again.

Finally, maintenance includes systematic inspection of the propeller hub (checking for fishing line wrapped around it, which can cut the seals) and annual replacement of zinc, aluminum or magnesium anodes depending on your navigation area, to protect your lower unit from destructive galvanic corrosion.

Equip and maintain your transmission system

To work efficiently in your workshop or boatyard, DAM Marine supplies all the required technical consumables. Lubrication and sealing quality allow no compromise. Check our categories to find bottom-fill oil pumps, drain plug seals (to be replaced each time they are opened), and water pump kits (turbine/impeller) that must be changed regularly. Explore our catalog to discover our full range of marine parts and validate your service kit at the best price, with express delivery so your boat is not stuck in the yard.

When should lower unit oil be changed?

The standard industry rule requires changing gear oil every 100 operating hours, or at least once a year during winterization preparation. It is essential to carry out this oil change before storing the boat for winter.

If, during draining, you notice “mayonnaise”-colored oil (water/oil emulsion), do not simply refill with new oil. Water has entered the housing. You must remove the lower unit, carry out a leak test, and replace the propeller shaft or water pump oil seals, otherwise you risk completely destroying the gear system during your next trip.

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Boat outdrive units

Embase bateau Johnson - evinrude

Mercruiser sterndrives

Embase bateau Mercury - mariner

Embase bateau Omc

Embase bateau Volvo penta

1907 item(s)

MERCURY BASE DRAIN SEAL

RÉF. AP0100 | EMP

Drain gasket for Mercury - Mercruiser outdrive.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€4.68 VAT included

€3.90 VAT excluded

MERCRUISER ALPHA ONE LOWER BASE REASSEMBLY GASKET KIT

RÉF. 28200 | EMP

Complete reassembly gasket kit for Mercruiser Alpha One base.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€10.68 VAT included

€8.90 VAT excluded

JOINT DE VIDANGE EMBASE HONDA

RÉF. 91301-ZW4-003 | HONDA

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€2.16 VAT included

€1.80 VAT excluded

MERCURY - YAMAHA 8MM BASE DRAIN SEAL

RÉF. AP2686 | EMP

Drain gasket for Mercury - Yamaha engine base.

Inner diameter 8mm.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€1.98 VAT included

€1.65 VAT excluded

MERCURY BASE DRAIN SEAL

RÉF. 27/8M0082880 | MERCRUISER

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€4.73 VAT included

€3.94 VAT excluded

JOINT DE VIDANGE EMBASE SUZUKI OEM

RÉF. 09168-10022 | SUZUKI

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€2.50 VAT included

€2.08 VAT excluded

VOLVO CARDAN BASE BELLOWS

RÉF. 182765 | ORBITRADE

CV joint boot for Volvo Penta SX - DPS and OMC Cobra drive including clamp.

Application :

OMC COBRA

DP-SM, DP-S, DP-S1, DPS-A

DPS-A OXi, DPS-B, DPS-B OX, DPS-B1

DPS-B1 OX, DP-SMTD, FWD, SX-A

SX-C, SX-C1, SX-C1AC, SX-C2

SX-CT, SX-CT1, SX-CT2, SX-M

SX-M1, SX-MTD, SX-MTD3, SX-R

SX-RT1, SX-RT2, SX-S, SX-SLT

TSK DP-S, TSK SX-C, TSK SX-C1, TSK SX-C1AC

TSK SX-C2AC, TSK SX-CLT M10, TSK SX-CLT1, TSK SX-M

TSK SX-MACLT, TSK SX-MBAC, TSK SX-MDA, TSK SX-MDB

TSK SX-MDC, TSK SX-MHP, TSK SX-MLT, TSK SX-R

TSK SX-R1, TSK SX-R2, TSK-A-32, TSK-A-32-NPT

TSK-A-42, TSK-A-42-NPT, TSK-A-52-NPT, TSK-A-AC-32

TSK-A-AC-32-NPT, TSK-A-AC-42, TSK-A-AC-42-NPT, TSK-A-AC-52

TSK-A-AC-52-NPT, TSK-A-OX-32, TSK-A-OX-42, TSK-A-OX-52

TSK-B-32, TSK-B-32-NPT, TSK-B-42, TSK-B-42-NPT

TSK-B-52, TSK-B-52-NPT, TSK-B-AC-32, TSK-B-AC-32-NPT

TSK-B-AC-42, TSK-B-AC-42-NPT, TSK-B-AC-52, TSK-B-AC-52-NPT

TSK-B-OX-32, TSK-B-OX-42, TSK-B-OX-52, TSK-C-32

TSK-C-42, TSK-C-52, TSK-C-52-NPT, TSK-C-AC-32

TSK-C-AC-32-NPT, TSK-C-AC-42, TSK-C-AC-42-NPT, TSK-C-AC-52

TSK-C-AC-52-NPT, TSK-C-OX-32, TSK-C-OX-42, TSK-C-OX-52

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€55.20 VAT included

€46.00 VAT excluded

VOLVO EXHAUST BASE BELLOWS

RÉF. 19848 | ORBITRADE

Exhaust bellows for Volvo Penta outdrives:

AQ200, AQ250, AQ270, AQ275

AQ280, AQ280DP, AQ290, AQ290DP

DP-A, DP-A1, DP-A2, DP-B

DP-B1, DP-C, DP-C1, DP-D

DP-D1, DPX, SP-A, SP-A/MT

SP-A1, SP-A2, SP-C, DP-E

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€56.40 VAT included

€47.00 VAT excluded

VOLVO CARDAN BASE BELLOWS

RÉF. 19294 | ORBITRADE

CV joint boot for Volvo Penta outdrive including clamps.

Premium quality.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€51.60 VAT included

€43.00 VAT excluded

OEM MERCRUISER CABLE BELLOWS

RÉF. 74639Q02 | MERCRUISER

Original Mercruiser OEM cable boot for Alpha One and Bravo outdrives.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€34.03 VAT included

€28.36 VAT excluded

JOINT OMC 0909515

RÉF. 33900 | GLM

Joint de carter intermédiaire pour embase OMC 400 - 800.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€10.80 VAT included

€9.00 VAT excluded

MERCRUISER CABLE BELLOWS BASE

RÉF. 34639 | EMP

Cable boot for Mercruiser Alpha One and Bravo outdrive including clips and clamp.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€21.00 VAT included

€17.50 VAT excluded

VOLVO EXHAUST BASE BELLOWS

RÉF. 182764 | ORBITRADE

Exhaust bellows for Volvo Penta SX - DP-SM and OMC Cobra outdrives.

Hose clamp included.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€55.20 VAT included

€46.00 VAT excluded

BRAVO BASE REASSEMBLY GASKET KIT

RÉF. 28400 | EMP

Kit joints de remontage complet pour le remontage de toutes les embases Mercruiser Bravo sur la platine.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€8.34 VAT included

€6.95 VAT excluded

VOLVO BASE AXLE BEARING

RÉF. 3853423 | ORBITRADE

Volvo Penta cylinder shaft bearing to be used in addition to bushings 3853424.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€6.48 VAT included

€5.40 VAT excluded

BRP BASE DRAIN SEAL

RÉF. AP0957 | EMP

Drain gasket for BRP and Volvo Penta engines.

Livraison express → Wednesday 08 July

Livraison classique → Friday 10 July

Commandez dans les

00 h 00 m 00 s

Disponible

€1.02 VAT included

€0.85 VAT excluded

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1907 item(s)

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Devis gratuit

Oil circuit

Upper Engine

Lower Engine

Exhaust

Electrical parts

Power steering and Steering

Filter by engine

Boat outdrive units - Reliable marine propulsion systems

Improve your boat's propulsion with durable, compatible outdrives

What is a boat lower unit and what is its role?

How to choose the right boat lower unit

Technical criteria: power, shaft and rotation

Compatibility with major engine brands

Signs of a worn or damaged lower unit

Maintaining your lower unit: oil change and prevention

Equip and maintain your transmission system

When should lower unit oil be changed?

1907 item(s)

MERCURY BASE DRAIN SEAL

MERCRUISER ALPHA ONE LOWER BASE REASSEMBLY GASKET KIT

JOINT DE VIDANGE EMBASE HONDA

MERCURY - YAMAHA 8MM BASE DRAIN SEAL

MERCURY BASE DRAIN SEAL

JOINT DE VIDANGE EMBASE SUZUKI OEM

VOLVO CARDAN BASE BELLOWS

VOLVO EXHAUST BASE BELLOWS

VOLVO CARDAN BASE BELLOWS

OEM MERCRUISER CABLE BELLOWS

JOINT OMC 0909515

MERCRUISER CABLE BELLOWS BASE

VOLVO EXHAUST BASE BELLOWS

BRAVO BASE REASSEMBLY GASKET KIT

VOLVO BASE AXLE BEARING

BRP BASE DRAIN SEAL