Did you use a lawn tractor combination transmission/rear end or a transmission AND a transaxle. I looked at a site or two for lawn tractor pulls which seem to be dominated by cub cadet rear ends and perhaps their transmission and jacked up Kohler big block engines.

I considered using a 35 hp OMC lower unit foward and reverse clutch dog gear set to drive primary var speed pulley but I had concerns about what torque it would take- a prop slipping in water and driving oversize tires didn't seem to be similar to me.

on these 4As, are the intake and exhaust manifolds shop built? is there an ideal length and/or ID for them?
How are carbs chosen and is there a closer to ideal setup?

You mentioned 2 cylinders earlier. I visit a govt liq site and at warner robbins AFB (GA), there are a couple of generator sets with a 2 cylinder engine that looks similar to the 4 cyl 4As. are you aware of what hp are those rated at?

It seems the 4A must be a very well built and dependable engine if one can install into a light aircraft with confidence.

I have seen the rotax engines. What other engine are used for the mini airboats?

I have 2 yamaha 650 engines with jet pumps I was saving for a lightweight small boat (15' - 16')...seems here in GA the river shoals and lower units do play well together.

Thank You.

the village idiot