Updated: Dec 9, 2022
While you are outside the boat this is the time to check these crucial parts of the boat’s machinery.
What you are looking for: damage, evidence of corrosion, excessively worn bearings.
How to look: Rudder: Sight both sides of the rudder and check for fairness of the surface (again, don't neglect the bottom). Check the rudder bearings by gripping the rudder and trying to lever it side to side - the stock should be snug in the bearings. If the rudder is fiberglass, sound it just like the hull. If the rudder is hung with pintles and gudgeons check them for corrosion, damage, or excessive wear by observation.
Propeller: The propeller should be smooth and free of pits or dings - run your hand over all parts of it. If it is a folding or feathering prop it should readily fold or change pitch with light turning pressure from your hand.
Shaft: Spin the shaft by turning the propeller. It should turn easily (if the transmission is in neutral) with little noise or play. Check the shaft bearings by gripping the propeller and alternately exerting sideways and up and down force. The shaft should be snug. It should also appear straight and true and be free of corrosion or significant scoring at the bearings. If there is a strut supporting the shaft also check it for straightness and evidence of corrosion or damage. For all the bearings look at them as closely as you can (use a light) checking for uneven wear.
When you are inside the boat return to the stern gear inspection by first examining the propeller shaft where it connects to the transmission with a coupling. Couplings come in a few varieties, for this inspection focus on the condition of the coupling - is it freshly painted or is it rusty and damp? Is it secure? Check the fasteners if you can get at them. If it has a key and keyway check that the key is present and snug and the keyway does not look worn. If there are set screws, look at their condition and check if they have mousing wire securing them. Shaft alignment is related to the coupling fit. If the shaft is noisy or the bearing is unevenly worn there may be evidence of a poor fit at the coupling.
The shaft should be examined for scoring or pitting. Where the shaft exits the boat it will pass through a stern gland. Like the coupling, stern glands come in a variety of configurations so focus on overall condition. Is it corroded, greasy, wet? If there is a flexible bearing tube are the clamps securing it snug and in good condition? Are the clamps doubled?
The rudder head and bearing tube (which houses the rudder stock) will often be difficult to view (particularly on sailing vessels), but a little time spent here will be worth the effort. Observe the structure supporting the rudder tube and the visible bearing(s). The structure should appear sound and the bearing not excessively worn. Turn the wheel or tiller and observe the turning of the top of the rudder stock. It should rotate smoothly and without excessive resistance. Some rudders will have a stuffing box where the rudder stock enters the boat, check this for staining that might indicate leaks.
Significant Findings: Rudder stock or shaft are sloppy in the bearings. The soundings of the rudder produce a dull thud. Pintles and/or gudgeons are worn or damaged. Obvious damage corrosion on rudder or stock. Bent stock. Evidence of leaking rudder stock packing gland. Propeller or shaft has significant damage, scoring or corrosion induced pitting. Shaft is not true. Loose shaft. Poorly fit or loose shaft coupling. Stern gland loose or in poor condition.