ALPHA GII WATER BASE TUBE
The DAM Marine catalogue brings together complete Mercruiser sterndrives and transmission components, in OEM original parts or certified replacement versions. Our stock covers every subassembly: lower unit, upper unit, transom assemblies, as well as seal kits and shim kits. Use our filters by serial number, model and ratio to isolate the exact reference corresponding to your propulsion unit.
We supply the essential spare parts for a complete rebuild. Because assembling a sterndrive requires micrometric precision, our parts ensure strict compliance with gear backlash, bearing preloads and manufacturer tolerances.
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Demandez le délai de réapprovisionnement et le tarif en cliquant sur le bouton « Ask for a quote ».
Un conseiller traitera votre demande dans la journée.
Demandez le délai de réapprovisionnement et le tarif en cliquant sur le bouton « Ask for a quote ».
Un conseiller traitera votre demande dans la journée.
Clutch cone for Mercruiser Bravo outdrive.
Spring set included.
Protective cover for Mercruiser Alpha One G1 and Bravo base cylinder shaft.
Dérive pour embase Volvo Penta de types :
280
280T
290
SP
Needle bearing and oil seals included.
Single connecting shaft for trim cylinder on Mercruiser Alpha one base.
Axis being closest to the hull 30 cm.
Remember to add the necessary mounting hardware.
The Mercruiser sterndrive is the heart of the Z-Drive system. It redirects engine power to the propeller while managing steering and boat trim through hydraulic rams. Rigorous identification of a drive requires reading the serial number, usually stamped on the port side of the upper housing.
This number determines the production year, rotation direction and, above all, the gear ratio. This data is absolutely critical: fitting a drive with an unsuitable ratio will distort the load applied to your inboard engines. A ratio that is too tall will prevent the engine from reaching its recommended wide-open throttle range, WOT, creating destructive overload on the engine block.
The sterndrive architecture must match the hull characteristics and navigation programme.
The Alpha and Bravo ranges differ in sizing, but above all in shift mechanism. Alpha One uses a direct dog clutch engagement. This mechanism requires an ignition interrupt switch to release tension on the gears during disengagement, and perfect adjustment of the lower shift cable, whose wear is a classic cause of breakdowns.
The Bravo series uses a friction cone clutch located in the upper housing, offering ultra-smooth gear changes and tolerating massive torque. For any replacement, browse our range of boat outdrive units assembled according to Mercury recommendations.
The Alpha One sterndrive underwent a major technical redesign. The second-generation Mercruiser Alpha drive, Gen 2, introduced in 1991, corrected Gen 1 weaknesses with reinforced shafts and, above all, a higher-volume seawater pump with a stainless-steel body, improving cooling under heavy load.
| Generation | Period | Specifications and clutch | Usual engine |
|---|---|---|---|
| Alpha One Gen 1 | 1983 - 1990 | Dog clutch, standard bellows, moderate pump flow. | Up to V8 5.7L, 260 hp |
| Alpha One Gen 2 | 1991 - present | Revised profile, resized high-flow water pump, reinforced fastenings. | Up to V8 5.0L / 5.7L, 300 hp |
The Bravo series has no water pump built into the drive, as it is mounted on the engine. It is available in three versions sharing the same upper drive but fitted with distinct lower units.
A Mercruiser sterndrive is exposed to gear friction, marine corrosion and heavy axial loads. Reliability requires annual removal. This dismantling allows inspection of the bellows, U-joint, exhaust and cable, greasing of the splined shaft to prevent seizure in the engine coupler, and checking engine/drive alignment with the dedicated alignment tool. Poor alignment quickly destroys the coupler and gimbal bearing. Also adapt your anodes: zinc or aluminium in salt water, magnesium strictly reserved for fresh water.
Draining the drive oil level is crucial. Milky oil, mayonnaise colour, confirms water intrusion. A pressure test must then be carried out to isolate the leak. On an Alpha, the water pump base is often at fault. On all ranges, check the propeller shaft oil seals, often damaged by fishing line, and the shift selector seal.
On the water, noises are valuable indicators: a cyclical rumble or sharp knocking when steering does not always mean broken gearing, but very often worn U-joints or a seized gimbal bearing. These symptoms require immediate immobilisation and removal of the lower unit.
Adaptation and repowering follow strict mechanical standards.
No. Shafts, gearing and water pump housings are completely different between an Alpha One drive Gen 1 and Gen 2. Tooth angle prevents any mixing of parts. You must order the exploded-view reference corresponding to your exact generation.
Upgrading a Mercruiser Alpha to a Bravo is essential when installing a very high-torque engine, such as a V8 Stroker. The operation is substantial: it requires complete replacement of the transom assembly because bolt patterns, exhaust and water inlet differ. Above all, because Bravo drives do not have an integrated impeller, this conversion requires adding an engine-mounted seawater pump, significantly affecting the price of your Mercruiser during a full repower.