On Wed, 15 Mar 2006 15:24:13 GMT, "Roger Long"
wrote:

I would never try to make hot water from the batteries through the
inverter for obvious reasons.

You don't say how big your battery bank is, and whether or not it is
isolated from your starting battery.

If you have an isolated house bank driving the inverter comparable to
4 golf cart batts (about 440 A-H), you could run the inverter/heater
for at least 30 minutes or so. I used to do that on my old boat if I
wanted to shower in the morning without starting the generator.

The important thing is to make sure you don't run down the starting
batt, and that you fully recharge the house bank as soon as possible.
I wouldn't worry too much about the alternators. They will generally
take care of themselves if the voltage regulator is working properly.

I agree with the others that there is some issue with your water tank
not being heated properly from the engine. Is the heating loop on the
raw water side or the fresh water side? It really needs to be on the
fresh water side to get warm enough.