I just bought a 1976 Spectrum with a Ford 460 inboard recently rebuilt with about 30 hours on it. It starts and runs fine out of the water. When I take it to the water, it will start right up and run fine. I can run about 8 miles upriver with no problems. But then it starts to run intermittently. It starts up, runs anywhere from 10 seconds to a few minutes (it seems the longer I wait the longer it will run, but not always). I changed the fuel filter. Carb was rebuilt recently with around 10 hours on it. May be overheating? The temp gauge hovers around the middle of 150 and 240F on the gauge. Some sort of electrical shutoff due to excess water in the bilge? Who knows?