I have a 2004 Yamaha waverunner xlt 800 that isn't running at full speed. It use to run around 60mph now it will barley run around 50mph. Acceleration and HP might be down a little but the top end speed is what I'm concerned about because it isn't running to par. We have changed the spark plugs before and it hasn't helped either. Any advise would help. Thanks.

SOURCE: I have a 2004 60

Every sympton you are describing here can be attributed to fuel starvation due to blocked jets and or water in carbs, when your engine dies does it die with dry plugs, or wet oily ones?

SOURCE: Waverunner will not start

Check the fuses under the front in a round cover, 1 fuse is for the starter,but the cover must be on after checking the fuses.

SOURCE: 1996 yamaha virago 535. no power on top end,50mph

1 st check compression on that cylinder by taking spark plug off and getting a compression tester and screw into spark plug hole then turn the engine over and if the compression goes over 100psi/7.5 bar then your ring are ok a picture below will demonstrate get back to me if the ring are ok i have more solutions

SOURCE: i have a 1998 1200XL yamaha waverunner. it was

check the exhaust manifold gasket so times they leak in to the hood are want ever and kills your intake air will not run up are take the seat off and run it if it run fine or better you found the problem

SOURCE: 2007 vx yamaha waverunner cruiser...

check the fuel positionong sencer that nmight mot b opening all the way