Servicing the Furnace

I got the back locker unpacked and squirmed down there to service the furnace. First thing that looked bad was a rusty screw on the cover plate. As of last month when I tried to start the furnace, it would not ignite. Last time that was caused by a dead compressor. The rusty screw was concerning, so as I'm removing the screws, I'm thinking that salt water dripped into the locker from the hatch and ran down the outside of the furnace and rusted the screw's locking washer.
I was very wrong. Once the cover was remove the insides of the outer case were covered with soot on at the bottom 2 inches of the case. The only way that could have happened is that an ocean wave hitting the back end of the boat washed up through the exhaust system, muffler and then poured soot in to the case through the boiler's fire chamber. Chances are water also washed up the air intake, but that would not have fill the outer case with soot.
I cleaned it up and then cleaned up the injectors. I could not see any water in the boiler fire chamber. I fired it up and she started with no problems.
On the way down here we ran the furnace for the first 3 or 4 days cause it was cold outside. After that we didn't run the furnace but that is also when we hit the really rough seas with swells above 16 feet. The cockpit also got pooped a couple time in that period.
The exhaust cover is rusted (that pissed me off since this is an ocean product, yet after only a day or two of exposure, the threads on the bolt are totally rusted and prevented me from installing the cover when we were in rough seas.) I have penetrating oil on it right now, but if it doesn't break loose, I'll have to use 3" blue tape to tape over the furnace air-intake/exhaust pipe when at sea.
I will fire her up completely tonight to wash dishes and shower. The furnace consumes .2 Gallon an hour of run time… much better than the engine. So if all you need is hot water, the furnace is the way to go!!! But for the last couple of months I've been using the engine to get hot water… while it also charges the batteries, there are time when all I want is hot water and do not the more power in the batteries.
It is nice to have multiple ways (redundancy) to get what is needed.