What temperature would it take with raw water to heat up a water heater tank? My gets to 135-140 if I motor for an hour or so.Also how fast does the electric heaters take to heat the water to the max temperature it will get to?
I thought as an option of using a generator to heat the water with the electric coil. I hear it stays hot for a long time even with out power to it.
1. Normal Universal engines for C30s were the M25 and M30 series with freshwater cooling systems and heat exchangers. The thermostats were either 160 or 180 F. That determined the temperature of the freshwater that was used to heat the HX inside the domestic hot water heater (not the engine HX, although, obviously, the engine's freshwater runs through there, too). It takes us about 40 minutes of motoring under load to get the domestic tank hot (6 gallons, Seaward tank).
2. The electric heaters take 15 to 20 minutes to heat the same tank. Don't need to leave the heater on all the time, all it does is overheat the water.
Depending on the tank and the insulation, it'll last for a few hours. Our experience is that with hot water in the tank at night, it's tepid, at best, by the time morning rolls around.
What we've done is simply change our routine. Instead of showering in the morning, we shower in the afternoon, or before dinner, when the engine has heated the water. We also have a solar shower which we can use inside the head/shower compartment/cabin on our boat, thus utilizing the shower drain instead of having to sit out in the cockpit.