I bought one a couple of years ago, plugged it into the boat's AC shorepower receptacle for battery charging using the 40-amp Smart Charger of Xantrex. As you said, it worked fine but I don't do it anymore. I opted for a solar panel (80 W) to charge at anchor with some diesel support at night. (I don't have large power needs at anchor--mostly just refrigeration.) Now (I as said earlier) if I use the generator for any AC appliance, I plug the appliance directly into the generator; do not run it through the boat's AC circuitry. BUT--long way around here-- I carry it on the boat principally for emergency use as a battery charger for a dead starting battery; all else failing!That little ($89 on sale) 800W two stroke is a straight generator. it is governed to 3600 rpm to produce about 60 hz. Those aren't as bad as it seems they might be. lots of "how-to" on youtube for a couple of small changes to make em work pretty well. LOUD .. yes.. not as bad as a weedeater but close
EDIT: It can push a good 40 ampere battery charger and would be fine if you were stuck somewhere with dead batteries.. Loud and a two stroke requiring oil/gasoline mix..
BTW--- I don't see the safety issue here w/ a gas powered generator used as described. After all, we already carry gasoline for the outboards. When the generator is running, I'm watching it and have an A/B/C extinguisher within arm's reach while it is running.