I have a 2000 Sunesta 232 Mercruiser 5.0. The boat runs fine for maybe 10 - 12 minutes and then loses power. Shutting it off for 10-15 minutes and it runs good at any given speed for another 10-12 minutes or until you throttle it back and then loss of power. the engine temp never exceedes 160 degrees. I have replaced the fuel filter, fuel pump, fuel cooler, fuel line and regulator ( no easy task) and have not corrected the problem. I have replaced the relays but have not tested it yet. Is the ECM the problem?