After a lot of research, I finally found a source for new heater cores for our old (300-H) Heatercraft heater boxes. The entire units (same old design) and cores (updated design) are still made under the name "Maradyne Marine". Unfortunately, I accidentally ordered two and don’t need one of them, so before I return it, I thought I would see if someone wants to buy it (for less than what I paid). It is new-in-box and I am selling for $85 via PayPal, shipping included (to lower 48 states).
It fits nearly perfect - the only slight modification I had to make was trim about 1/8” off of the small bracket (as seen in the pics). Took me about 15 sec. with tin snips. I just tested it out yesterday and it works the same as the old core (without the leaking!)
PM me if interested.
