Both furnaces had ingested so much salt water through the exhaust that they were corroded into a mass of gunk inside. That meant having to purchase two new furnaces for 6 more BOAT units! OUCH! The forward unit that heated the staterooms only had 27 hours of run time on the furnace and it was now nothing more than a high priced brick.
After the shock wore off, I installed the two new Wallas furnaces (40dT’s). Having the power, fuel and ducting already run (although some of the ducting was also wrong) helped immensely, but replacing and re-engineering the exhaust tubing was quite a job. It took me a couple of days to get the new thermostats installed, new exhaust installed/insulated and everything up and running.
The good news is that I like the new Wallas DT units much better than the older D units. They bring in fresh air and heat it, helping to keep the boat dry. I had Wallas heaters on all three of my dive boats (including the Dive Charter Boat) and always marveled at how well they would defog the windows even with 14 dripping wet divers huddled in the cabin.