[tevake]

I mentioned this earlier, but with a
35 mph speed limit, wow! How many miles of road are there on the island?

This could be a perfect setup for an electric vehicle.

Put the $s you were thinking of using for the conversion to petrol power.
Into a solar system and batteries in your home there for when the power is out.

Is there a particular reason you don't want an E V. ? Even if it fits your situation nicely?

A friend on Kauai got himself a Chevy Volt and put in a solar system at home. Almost never uses the gas engine in the car, and saves on his electric bill at home besides charging the car. Kauai is a much larger island with higher speed limits, EV works there.

Cheers Richard