Which you've probably never heard of, but the trucking industry seems to love them. They're designed to run on standard diesel fuel and used to heat truck cabs or cargo spaces without idling the motors. I've spent the last 3 weeks researching everything that burns diesel (highest BTU/gal fuel) and could be used as a boat heater.
Max output of 13500 BTUs, 10 heat output settings, adjustable 65 CFM fan speeds, .06 to .12 gal/hour fuel usage, ultra quiet, easy on the batteries, included thermostat that has all kinds of functions (timer, etc), and a 2 year warranty.
And they only cost $1795.00 from Cummings NW on Commercial drive (same price quote that I got from a distributor in the lower 48). I put my order in today.
I'll have to adapt a bit for a boat usage, but they're built like tanks and can handle severe bouncing around while operating.
Considering what the other models cost (of equivalent BTU output) and its capabilities its a dang good deal.