Don’t Forget the

Drive Train

By Allan Derickson

Cruising World April 1990

While most of us understand the need for proper engine maintenance, we often neglect the components that deliver the horsepower to, the propeller: the shaft, shaft coupling, stuffing box and stern bearing. These are critical elements of the drive train, whose failure can mean anything from inconvenience to catastrophe. Because they are hidden away in dark cramped recesses, they often don't get the attention they deserve.

If your boat suffers from excessive vibration under power or has chronically wet bilges, the cause may be drive train related. Excessive vibration can also come from loose engine mounts, poor engine performance or propeller fouling. However, if your engine is well bolted down, runs smoothly in neutral, and the propeller is clean, suspect the drive train. Contrary to popular opinion, bilges should normally be dry; a wet bilge may contribute to hull blistering. A common cause of wet bilges is a loose stuffing box. Later I will explain how it should be adjusted. First we will conduct an investigation of the entire drive train, beginning at the aft end, and correct any deficiencies as we go.