I didn't spend a lot of time studying the manual ( LINK
) and I've not seen or heard anything about this water heater, but from what I can tell, it seems like a good appliance for what you need it for.
You have to use it very carefully onboard however, since it's designed for use at a campsite - outside, in open areas. Since the device lacks means of exhausting CO gases, the use of it in the cabin could result in CO poisoning. Additionally, if used in the cockpit, make sure there is a means of expelling any propane leaks which may occur. Propane is heavier than air and is highly explosive - not a good thing to happen in a contained space, especially with a combustion gas engine nearby.
However, an on-demand propane water heater is a great way to provide constant hot water, if used according to ABYC standards. Our last boat had a built-in system combined with a very large water tank (140 gal). We enjoyed unlimited hot water away from shore power without any issues. Of course, it was equipped with all the necessary and legal safety features.