How to Measure for Outboard Shaft Length

An outboard boat engine is designed to be mounted off the transom, at the aft of the boat. The shaft, an arm that connects the engine to the propeller, runs down from the engine into the water, where the propeller rotates to push the boat forward. Outboard engines come in long- and short-shaft configurations, with a measurement of the shaft taken in the same manner for both designs.

• 1

  Pull the shaft full out of the water.

• 2

  Place one end of the measuring tape at the edge of the transom mounting-clamp bracket. This is found where the engine meets at the transom of the boat.

• 3

  Extend the tape down to the cavitation plate above the propeller. This is the metal ridge over the top of the propeller blades that extends out from the shaft.

• 4

  Take the measurement off the tape measure between these two points. This is the shaft length.