bligh wrote:
Hi, I searched for a while but found no cost comparisons.

It's like doing homework.

... I'm looking
at the Force 10 6k btu model for an uninsulated 23' fiberglass boat
of approx 900cf. It comes in two different models. Is gas cheaper than
diesel in terms of operating costs?

Depends very largely on whether or not the boat already has diesel
tanks. If yes, then putting in a diesel line to the heater is a bit less
trouble & money than putting in propane. OTOH if you can tap a propane
line to the stove then that might be easier.

In terms of $$/btu I think diesel wins but that is a small factor unless
you live in a very cold climate

... Also, many people said neither
fuel will dry the boat out. I don't quite understand how something can
produce heat and not dry things out but I'm sure anything's possible
these days.

Hydrocarbon fuels (almost every type including gasoline, diesel, and
propane) are combinations of hydrogen & carbon, with slight amounts of
various other stuff mixed in. "Burning" is a process of combining it
with oxygen... same thing your lungs do. Combining carbon with oxygen
produces CO2, like you exhale, and CO, which hopefully you neither
exhale nor inhale... and H20, which you also exhale but hopefully don't
inhale! Putting H2o vapor into the air makes it damp, voila.

The answer is to have a chimney which carries the CO and H2O outside the
boat's cabin. Thus youo get heat with no damp. However those pocket
heaters & freestanding floor heaters put moisture into the air and can
actually result in a boat that feels clammy & chillier than before
lighting the heater.

A chimney on a boat is kind of a PITA. It often leaks and it tends to
catch toes & lines. But there are ways to minimize this kind of trouble.

Fresh Breezes- Doug King