I don't think you will find one specifically made for boats anymore. At best you might find one for an RV. There used to be a couple of outfits that made on-demand propane hot water heaters for boats but I think the liability issues drove them out of the market. I think Wolter and Polamar (or some such name?) made them at one time.
SailorMitchSailing winged keels since 1989.
1.20.09 Bush's last day the end of an error !! Hopefully we still have a constitution and economy left by then.
"Compassion and tolerance are not a sign of weakness, but a sign of strength." The Dalai Lama
good planets are hard to find-- a song by steve forbert
I have but one lamp by which my feet are guided, and that is the lamp of experience. I know no way of judging the future but by the past.-- Patrick Henry.