I'll follow this, as I have the 12,000 BTU model, and it's about the same vintage.
Have you considered corrosion at the leads creating heat and resistance at start-up? Those units eat a vast amount of amps in the first couple of seconds of running and I suspect if the wiring is compromised in any way, heat, and not cool air, would result.
Do you have a March pump in the same compartment bringing in the raw water? That could be a place to look, as they draw a large AC load on start-up, and could be strained if there was a marine beastie stuck in the circuit.
This is my model: http://www.mmair.com/marine_division...ir_conditioner
and this is my pump (a great pump, by the way):
* Liquid cooled, Maroon epoxy encapsulated (open air or submerge)
* 3/4" Inlet, 1/2" outlet (5/8" hose)
* 1/20 HP motor - 2.2 amps @ 110v
* 220v available - 50hz OR 60hz needs to be determined