How to Find Your Shaft Length


Short, Long, or XL?

One of the most common questions we get asked is how to know the shaft length of an engine? This is easier to tell than it sometimes seems.


When an engine is referred to as a short shaft, it's considered to be a 15" motor. Long shaft is considered 20”. An XL shaft is 25". In rare cases, mostly in big saltwater models, engines were made in a 30" shaft, or an XXL.

In none of these cases is the shaft length exactly 15, 20, or 25 inches. It's generally a measurement that falls closest to the number. To be clear, if I take a lower unit off and measure the driveshaft at 17", that would be considered a short shaft, being closest to 15 inches.

If you are measuring for a lower unit replacement and your original lower unit is off of the engine, simply measure from the top of the waterpump to the top of your driveshaft. A shaft length that falls closest to 15 inches is short, closest to 20 inches is long, and so on.

If your engine is mounted on a boat or a stand, locate the transom bracket of your engine and use the guide below to measure.

How to Measure

diagram showing how to measure shaft length

Shaft Length Guide

  • 15" = Short
  • 20" = Long
  • 25" = XL
  • 30" = XXL