I have a 1984 2.5 L Omc I/O. The boat ran fine for 2 hours then all of a sudden at high speeds only the engine started bogging down. It did the same thing 1 time last fall. At that time I changed the fuel flitter and did not have any problems until today. The boat did sit for 7 weeks with a 3/4 full tank of gas. While it was happening I noticed the voltmeter only reading 11 volts. I put a load on the system by adjusting the trim and the bogging down got worse. Any Ideas where to start diagnosing?