Shaft seals

No shaft seal can work trouble-free if the engine is out of alignment. Alignment should be checked any time rope, netting or a plastic bag binds hard on the propeller, and after any work on the drive train. Alignment is best done with the vessel at rest in the water. Alignment is not difficult, but does require careful work and patience. Small changes to engine height on each engine mount, and notes, helps avoid making alignment worse. If in doubt, this is one procedure that is probably better tackled by a marine mechanic.

TRADITIONAL STUFFING BOXES

These need regular inspection and adjustment. Check the condition of the heavy rubber hose and the hose clamps. The hose is subject to rotational stress (caused by the friction of the packing on the shaft). Failure of the hose could flood the boat. The packing gland will need periodic tightening as the packing wears, and replacement when there are no more visible threads to allow tightening. About 6-10 drops of water per minute with the shaft turning, and no drops at rest, will avoid the twin troubles of overtightening and overheating. An easy way to make small adjustments is to mark a reference point on the top of the packing gland and adjust 1/12 at a time.

DRIPLESS SHAFT SEALS

Overheating is the main enemy of both face and lip shaft seals, caused by either an airlock or lack of cooling water (in some models). Sand or weeds can also cause leaking. Models with no air vent need to be burped when the vessel goes back into the water (by squeezing the bellows or pulling it back to allow a little water to flow). In addition, the rubber bellows (and hose clamps) should be kept clean and inspected for any signs of deterioration or cracking.

CUTLESS BEARING

Some wear to the rubber sleeve over several years is normal. Any noticeable deterioration from the previous inspection from photos or notes in the maintenance log should be investigated and the root cause identified and corrected before the cutless bearing is changed. Unequal wear forward and aft or side-to-side may be a sign of engine misalignment. Leave 5cm between a shaft anode and the bearing so that it doesn’t block the flow of water – the ribbing inside the sleeve is to allow cooling water to circulate.