How is true diesel any safer for marine applications? Don't you have a gasoline engine already on your boat? Even diesel fuel is flammable - it just has a relatively higher flashpoint.

If you must have an oil-burner for some reason, do a quick search for Bio-diesel. There was a report some months back about a guy converting glow engines to run on this stuff - supposedly no ether required. I'm somewhat skeptical of that claim, but you never know.

Check out this source for Bio-diesel:

http://www.hiperfuels.com

He is actually local here in Houston, and I've been buying methanol and nitromethane from him - very nice guy to deal with. Never did ask him about Bio-diesel, though.

I agree with everybody else that the Ryobi 4stroke engines are your best bet. I have two in my garage for actual weedwacking duty, and they really do sip gas ultra miserly.