SkipperDoug - I have a Force 10, but it doesn't heat very well, as my engine is raw water
cooled, and only heats to approx 130 degrees, instead of 180, or so. Then there would be loss in the tranfer of heat.
Re: your issue - A friend of mine has a fresh water cooled Yanmar
. His old water heater died, so he replaced with a Force 10. He could get hot water, until he took off the anti-scald valve all together, and ran directly into the hot water in (as the unit came a couple years ago before the anti-scald device). He said it made a big difference. Although he claims his old, different model worked better, and kept water hot longer (ie still had warm water in the morning)
Of course, if removing the anti-scald device, you would have to be careful it wasn't too hot at the taps - especially if there are kids
*** I am not recommeding this, just passing on Friend's solution****