Seems like I am jinxed with 16000 BTU Marine Air Units...I have an approximately 2000 model, so 7-8 years old in a 37 foot gulfstar. Unit installed under vberth, worked fine until the other day...I had left it in heat mode for a couple of days, came back to the boat to find it off, the main internal panel breaker for the boat thrown as well as the a/c breaker. Tried reset, both breakers trip again. In troubleshooting, I find that I can get the fan to work (Passport II digital control model), but if I try to get it to heat or cool, it trips both breakers. I think it is when the compressor tries to start, as I hear the reversing valve reset, nothing happens, then bam, both breakers trip. Nothing else trips the breakers, so I am reasonably sure the breakers are ok. I'm thinking locked rotor on compressor, or ??? My question is, is it worth replacing compressor, or does anyone think I have a control box problem. I had an older marine Air unit in another boat that I actually fixed the circuit board on (helps to have a EE for a friend), but this seems like a different problem, since the breakers are tripping..can the circuit board cause this sort of problem? I am having difficulty seeing how a circuit board could cause breakers to trip..any help appreciated...I especially need troubleshooting tips..Anyone got any ideas?