1989 thompson daytona 27 with twin merc 470 4cyl... I am loosing power in one of my motors. the day starts off fine I usually cruise at about 3200 rpms about 22mph. The throttle for each motor is a little less then half way down. As the days goes on I have to push one of my motors to maintain the same rpms. By the end of the day I have one motor pinned down full throttle just to keep it at 3200rpms while the other motor still sitting at about a quarter throttle. I thought it may be a cable however I took the engine cover off and when I give it gas the cable moves and it opens the carb all the way. I have had boats with bad carbs but usually when I floor the gas it bogs out cause the carb cant keep up dumping fuel. basically I could have my throttle pinned and I am getting the same rpms as I would having it half power. Why it gets worse as the day goes on is a mystery to me.. my thoughts are maybe the points? a filter somewhere?
