12 volt generator?
 

So I am tossing around the idea of installing an inverter for ac power on the go. I have a generator (an older onan). My issue with the generator is how unstable the voltage is. I am thinking about removing the actual generator and installing a high output alternator to the onan 18 hp engine. Any thoughts? I already have a four battery system that splits by a switch and can be charged independently from the main engine with an isolator. That way I could still run everything from the generator engine rather than running the main engine.

Dodger

Your idea sounds good. Also, Honda & Yamaha both make inverter-generators that have a load sensing module. They run a little above idle under light loading and increase RPM as the load becomes heavier. You might want to consider one of these as they're designed from the ground - up for inverter output. With the load sensing module they also operate fairly economical (and they're quiet).

While purchasing a new generator would be the easiest option, I have already pulled the AC head off mine and made a mounting plate for two alternators. So far the only hold up is a pully for the engine shaft. Although I have heard that a small engine repair shop in town has a few different ones, just haven't had time to run down there yet. I will take some pics of it.

I believe that as the amperage on alternators heads north of 50 single belts will start slipping. Double pulleys of greater quality are required. Remember all this from the marine world.