My 1987 Yamaha 40hp 3 cylinder outboard runs at about 4400 RPMs at full throttle. The max RPM range is 4500 to 5500. It seems like I need to get a lower pitch prop, but sometimes when I hit a wave hard, the motor will open up and run at 5300-5400 RPMs for a minute or so and then drop back to 4400. Any ideas why the hard impact would make the motor open up? It seems like it may be a fuel problem but I tried squeezing the primer bulb when running at 4400 rpm but the bulb was firm and had no effect on the engine. Although, I did notice that the carbs were leaking some fuel last time out. The boat is somewhat slow to get on plane but not terrible. The butterflies in the carbs are almost horizontal at full throttle. They are slightly angled upwards, but not by much. The spark plugs all look good, they are somewhat new and dark brown. Please note that this motor has 3 carbs. Thanks in advance.
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