Chippawariverrunner,

Welcome to the Mini Airboat Association forum.

It sounds like you'd got a lot of aviation fabrication experience. I'm betting you can make a NICE Mini Airboat.

Papee gave you some good advice. Listen to him. He's been there, and done that. You can learn from him.

Here's MY 0.02 worth:

Honestly, a 48" wide hull is on the narrow side. Yeah, it CAN be done. But it WILL be VERY unstable. You'd be safer with either a much wider hull, or a much narrower prop.

To put a 72" prop on a 48" hull would be asking for a lot of trouble, IMO.

I assume that your Alumicraft hull is a typical wide Jon Boat, which has strakes/ridges in its bottom. There have been many small airboat built that way. It all depends on what you expect of it.

If you want a boat to just putt around in, it'll probably be O.K., IF you reduce the prop to about 42".

IMHO, you'd be better off to get a different hull, one that is meant for airboat use.

The Generac engine is kinda' new to the Mini Airboat world. Reviews are mixed about it.
But if you intend to use a 72" prop, you'll HAVE to use a reduction drive.

We have a member who's been working on a souped up Genarac.

Hopefully he'll chime in before long.

Anyway, WELCOME to the forum.

Duane