[travlin-easy]

Ditto! Not much at all from the exhaust waters, which I can put my hand in without being close to getting burned. I believe your best bet would be to place an automobile heater core in line with your freshwater heat exchanger. It would work just like a car heater, maybe even better. And, you'll have a fan for circulating the cabin air if you rig it properly. You can find the heaters at JC Whitney, or most auto junk yards, and they're not very expensive. Replacement Direct Fit Heater Core - JCWhitney

Good Luck,

Gary