I agree with Martin...Lou, you CAN get a permit to work without much of a problem, and you CaN set up a business to repair marine engines, especially if you are able to bring the software to diagnose Etec, Suzuki, and other computer driven powerheads. There is a need for a qualified diagnostician that actually lives on the island. As it stands now, an owner of a computer driven engine has to fly the tech out just to check the program, this gets expensive quickly.
The key is to make sure that you can adapt to the special society that exists here on Ambergris Caye. I come and go quite a bit, but would be able to stay put easily...hopefully you will find your niche.