Motor length?

I have three motors to go look at soon and can't pass up a deal like this, but since my boat didn't come with a motor and I know I can get a 40HP on it with no problems. How do I figure out the length of the lower end? Do I need to take to a dealer and he can figure out or is there something I can do to figure this out? The back end looks like this ..

First you want to measure the transom height of your boat.



Then you want to measure the motor the shaft length of the motor you intend to buy. The shaft length is the distance from the inside top of the clamp, to the cavitation plate which is the flat plate right above the propeller.



The motor shaft needs to be as long or longer than your transom height or you will have to make modifications to the boat or the motor. Hopefully the motor you find will have the same length shaft as your transom or be just an inch or so longer than the boat is high.

Thanks Mike, I've been out of the boat building for 12 years and I knew I was forgetting something. Thanks for the info and I HOPE [-o< that the three motors are going to be good ones. \/

Measure the transom height and then you can add an inch or 2. They make the plates to lift your motor or drop it. I run a long shaft (20") on a short transom Jon boat (16") but I have a plate to raise my motor. The sketch should be about even with the bottom of your transom to reduce drag.

see attached