Heat on the boat is a really really nice to have. Saved our bacon a few times and I'm sitting here in Middle River MD where it's been 30 F at night and blowing hard. That little electric heater doesn't cut it here and I can't use it when I'm anchored out or sailing.
Back in 2015 I installed a Wallas 30D diesel heater that I purchased used on Ebay on Skylark. This unit got damaged so I replaced it with a new 22DT also from Wallas. I had some problems with the 30D as the transistor that operated the glow plug burned out several times. I chose to stay with the Wallas as they use a direct vent system and that made installation in a VERY tight space possible. Specifically it let me route the exhaust hose much closer to combustibles (like fiberglass) than a regular exhaust. I wanted to exhaust through the transom, not on deck.
Anyway, the 22DT worked great for a while but then started blowing exhaust into the cabin. One of 2 studs that hold the burn pot together had rotted off. The heater might have gotten wet in Hurricane Florence when Skylark was in New Bern. I fixed it by welding a new stud in. About a year later, same thing, other stud. I welded it, but this time I guess I was in a hurry so I only removed the electronics from the unit so they wouldn't get fried, I left the little hypodermic needle that injects the fuel. It roasted. Luckily I had the old 30D lying about so I used that one. Unfortunately I didn't think to clean it out at the time. Last night I noticed the heater wasn't blowing very hot, just warm and very early this morning I discovered the heater had shut off. Uh oh. So I guessed right and found the hypodermic completely clogged, cleaned it out, reassembled and it's toasty in here.
When Tom and I sailed down here the heater worked well...until it didn't. At that point it wouldn't start and we traced it to air getting into the fuel line at the filter connection.
So it's been kind of a love/hate relationship with this thing. It seems a little tender and sometimes I'm worried about it but it fits in a really tight spot and it's awesome when I push the button and the boat gets warm.