TOPIC: 1962 Lark for MFG

Hello and Thank you for previous help.
I Just bought a 1962 Evinrude Lark for a 1959 MFG Celeron. It is a short shaft, 17" from bracket to cavitation, and the boat transom is 20". Should I go with a long shaft? Will the weight of the boat and motor put the prop under water? Thanks again, Paul

You MUST convert to long shaft. This is realy easy to do. I probably have the parts you need. You can't run a 15" leg on a 20" transom any more than you can run a 20" leg on a 15" transom and have it perform.

Thanks for responding. 17" on 20" transom is what I have. 2" or so, I've read, is acceptable. No?

Paul, I believe the general consensus on the motor height subject is having the anti-ventilation plate (commonly called cavitation plate) 1" above the bottom of the keel is optimum. Going to 2" is possible on some applications, but not all, and risky on starving the water pickup for cooling the motor. 3" (20-17=3) is asking for trouble! It's not so much will the prop be in the water, as will the water intake for cooling stay in the water. The motor will sit lower in the water when sitting or idling, but once you accelerate to plane the water will only rise about an inch from hull height before it gets back to the motor. If the pickup point for cooling water is not completely submerged, it will suck in air instead of water, and an overheat condition and motor meltdown will be inevitable.

You can check this by hanging the motor on the transom, use a straight edge on the bottom of the hull projecting back to the plate area. Take your measurement and see where you are.

If I've mis-stated or given bad or confusing info here, someone please feel free to correct and or clearify further.

Mark, Your explanation is very clear. I'm new to outboards and hadn't thought about all of the factors involved. Crosbyboat has advised that shaft conversion would be easy. I hope so. This is a 40hp Evinrude Lark IV manual, not selectric. Now to find parts and an experienced mechanic to help out. Shouldn't be too hard here on the coast of Maine. Thanks to both you guys.