Marine Propellers

It is a good idea to remove the propeller from time to time, to stop it seizing solid on the shaft. This is particularly important in the case of outboard and outdrive propellers, which usually have either shear pins or flexible hubs that are designed to protect the engine and transmission by slipping or breaking if the propeller hits something. Unfortunately, after a period of time, these protective devices break of their own accord, so it's important to make sure that the propeller can be taken off and replaced at sea.

Removing yacht propellers

Straighten out the legs of the split pin and remove it, or flatten the lugs of the tab washer that holds the propeller nut in place.

Use a block of wood to stop the propeller turning and undo the propeller nut.

It should be possible to pull an outboard or sterndrive's propeller off the shaft by hand. Make note of the order that any springs or washers come off, and which way round they go.

The best way to remove a stubborn propeller is with a puller. Once the puller has been tightened, a few light taps with a hammer on the puller should make the propeller slide off.
As a last resort, try warming the propeller boss with a blow lamp.

Propeller repair

If necessary, use a file to smooth any burrs or nicks from the edges of the propeller, but be careful not to remove so much metal that there is a risk of the propeller becoming unbalanced. If it is badly damaged refer it to a propeller repair workshop.

Replacing propellers

Before replacing the propeller, grease the shaft with a non-graphite grease.
Slide the propeller back on, making sure that any keys, shear pins, springs or washers are replaced exactly as they were removed, but use a new tab washer (if there was one) to hold the propeller nut in place.

Tighten the propeller nut just sufficiently to grip the propeller, then insert the split pin (if there was one). Bend up one tab of the tab washer to hold the nut in place, or open the legs of the split pin and bend them round the nut.

Stern glands

Greasing stern glands
If your stern gland is fitted with a greaser, routine greasing involves either turning the handle or tightening the cap by one turn after every few hours' running: once every four hours is about right. Eventually, this will use up all the grease, which will have to be replaced. Don't use graphite grease: its carbon content causes extremely rapid corrosion in the presence of salt water.
Remove the top cap of the greaser. If yours is the type that uses a handle like that of a garden tap to operate a plunger, 'unscrew' the handle to return the plunger to its starting position.

Invert the grease can, so that the hole in the plastic disc is over the greaser.

Press the whole can downwards, so that the plastic disc slides into the can and forces grease out. You may have to stop a few times, especially when the greaser is nearly full, to allow trapped air to escape.

Replace the cap of the greaser.

Adjusting stern glands

With the engine stopped and out of gear, turn the shaft by hand to get a feel for how stiff it is.
Slacken off any lock-nuts holding the two parts of the stern gland together.

Tighten the clamping bolts that hold the two parts of the stern gland together, or screw the sleeve into the outer casing. Don't tighten them by more than half a turn at a time, and - if yours is the type that has two or three bolts - make sure that you tighten them evenly.

Turn the shaft by hand and check for drips: it should turn freely and leak between one and six drips per minute. If it is leaking too quickly, repeat.

Outdrives and saildrives

Outdrives and saildrives circumvent the need for a stern gland altogether by - in effect - extending the gearbox right into the water in the form of a drive leg. Of course, this doesn't make the problem go away altogether: it just changes it a bit, because instead of having to seal the gap around a small rotating shaft, there's a much bigger hole to plug between the hull and the drive leg. Outdrives achieve this by using flexible rubber bellows between the transom and the leg, while saildrives use a rubber diaphragm to seal the joint between the drive unit and the bottom of the boat. Servicing recommendations vary depending on the manufacturer and model, but the importance of following them to the letter is obvious.

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