Greetings;
I bought a used cheap lower unit for my johnson awhile
back. Since boating season is coming I thought about
getting it ready for the season just in case my old
one craps out. When I put a spare prop on I
realized that its a 13 spline shaft on it and My other
one (primary) has a 15 spline shaft on it.

Now I am looking at this lower unit wondering if it
would even work on my Johnson 175.

The casing looks like it would bolt right on. (same size)

What kind of Johnson motors used a 13 spline shaft?

HELP!

Thanx.
Tom