I got a 2007 90 Yamaha 4 stroke. It normally runs about 5600 rpms at maybe 23 - 24 mph. Ive done changed fuel filter, spark plugs, fuel line and added some sea foam. It had a little bit of gas in it from last year but I have added fresh fuel to it twice in last 2 r 3 months. This last weekend it only would run 4800 rpms at 19 mph.same prop .cranks good and runs fine at low speed..what do you all think is the problem...What else can I do to fix it,,,,,thanks.
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