Science of Silence


How does it solve shaft alignment problems?

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. All this takes hours of painstaking work. And then when you launch the boat, or tighten the backstay on a yacht, it all moves slightly and needs to be done again!

The 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.

Can the engine be installed flat?

Marine engines are normally lined up with the propeller shaft, which has to angle down through the bottom of the boat. The engine therefore ends up with its front higher than its back, wasting precious headroom. Fit an Aquadrive between the engine and the shaft and suddenly you have an angle of ten degrees or more, allowing the engine to be fitted horizontally. The Aquadrive thrust bearing takes the propeller shaft (and the thrust!), and the special drive shaft is simply installed with the desired angle at each end. The maximum angle depends on the shaft speed.

Will Aquadrive help me re-engine?

The biggest problem 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.

How does the Aquadrive help with older boats?

Older boats have two particular problems, both of which make life a misery when re-engining. The stern tube and shaft are rigidly mounted in the hull, so the extra vibration of a new and flexibly mounted engine will simply destroy the sterngear. And older hulls, particularly timber ones, flex a great deal in the water causing the engine alignment to change. Aquadrive solves both problems by allowing free movement between the engine and the shaft. The movement of the new soft mounts, and alignment changes due to hull flexing, can be ignored.

Do I have to install the Aquadrive CV shaft joints with an angle?

Only on the larger CV shafts where it is crucial the CV shaft joint balls move in their tracks to spread the grease to maintain lubrication of the balls and tracks.

Can I get spares for my Aquadrive?

Yes, a full range of spares are available or we can rebuild your old unit.

What is the maximum angle per CV joint on the Aquadrive?

8° depending on which joint , only the smaller joints can have 8°. If you require more than 3° per joint ask us to carry out the GKN expected CV joint life calculation, this will ensure we specify you with the correct CV Shaft for your installation.

Installation of the bearing assemblies HDL 680, HDL 700 & HDL 780

These units use resilient mounting bushings that compress to the required setting when the mounting bolts are tightened to the correct torque setting. (See table of bolt diameters at back of instructions).

After tightening, check that the bushings compress equally.

Installation angles of Aquadrive CV shafts.

CV 42 (HDL 600) & CV 60 (HDL 700)

Aquadrive can be installed straight “in line” or with the constant velocity joints running at angles within certain permitted limits.

Max recommended angles are dependent on the power being transmitted and the maximum shaft speed.

It is important that neither joint exceeds its maximum permitted angle. While there is no need to run the two joints at equal angles, it will obviously prolong the life of the CV joints to do so.

For full details on installing Aquadrive, please see the Aquadrive product manual, which can be found in the Download section of this website.
The taper roller thrust bearing assemblies may eventually require greasing with an EP bearing grease at long intervals, dependent upon shaft speed. Do not add grease too soon - damages could occur.

Your local distributor will advise on this and on any maintenance required to the Aquadrive CV joints. (Usually, joint maintenance is only required on commercial craft with high annual service hours).