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How to Measure a Long or Short Shaft Outboard Engine

by Will Charpentier
Large outboard boat motor above the water.

Large outboard boat motor above the water.

An outboard might come equipped with a short shaft, a long shaft or an extra-long shaft, the shaft being the driveshaft that connects the powerhead -- the engine -- to the lower unit, where the propeller shaft, the propeller and the forward and reverse gears all live. Driveshaft lengths are standard throughout the boating industry. A short shaft is 15 inches long, a long shaft 20 inches long and an extra-long shaft 25 inches long.

Short or Long -- or Extra Long?

Measure from the bottom of your outboard's engine compartment down to the bottom of the cavitation plate -- the horizontal metal wing above the propeller. If the measurement lies between 19 and 21 inches, it's a short shaft. If it's about five inches longer than that, it's a long shaft. If it's about 10 inches longer than the short shaft's 20 inches, it's an extra-long shaft.

About the Author

Will Charpentier is a writer who specializes in boating and maritime subjects. A retired ship captain, Charpentier holds a doctorate in applied ocean science and engineering. He is also a certified marine technician and the author of a popular text on writing local history.

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