Science of Silence

Shaft Alignment

Marine engines are supported on timber or steel bearers fixed into the hull. These bearers are positioned to allow the engine to line up 'roughly' with the shaft. The engine is then adjusted on its mounts so that it lines up with the propeller shaft coupling within a few thousands of an inch. It's a three dimensional process involving the alignment of the engine's height, pitch and raw relative to the prop shaft - all of which this takes hours of painstaking work. And then when it comes to launching the boat, or tighten the backstay on a yacht, it all moves slightly and needs to be done again!

An Aquadrive changes all the rules. The propeller shaft fits into the Aquadrive's thrust bearing, which is fixed firmly into the hull. The engine is connected using the Aquadrive's special drive shaft. This allows misalignment of 12.5mm (1/2") or more on larger Aquadrives. Engine alignment can even vary while running, so the movement on an older or timber hull is not a problem.

An Aquadrive will even take up an angle of up to 10 degrees, allowing in some cases for the engine to be fitted horizontally. This eliminates the need for engines to be angled down in order to line-up with the shaft, which often means that the front of the engine is higher than the back, wasting precious space. It should be noted that the maximum take-up angle of an Aquadrive depends on the shaft speed.

Those wishing to re-engine their boats will appreciate the advantages of an Aquadrive system, since one of the biggest problems in choosing a new engine is fitting it in the existing space, with the fewest possible changes to the craft. Just imagine the flexibility if you could put an angle between the new engine and the existing shaft. Or use a longer Aquadrive to lower the whole engine. Or fit the Aquadrive to take out movement between a new engine with flexible mounts and traditional solid sterngear.


Twenty years of development has produced a range of modular Aquadrive units to suit shaft diameters up to 40mm and for engines delivering up to 2000hp and engine turning over up to 2300rpm.

Aquadrive's special long drive shafts allows for a greater flexibility when it comes to positioning the engine. Shafts up to 4 metres long allow engines to be raised or lowered relative to the propeller shaft, or even moved over to one side.

To view the Aquadrive product range, then please click here.