yamaha 70beto wont go above 4200rpm underload

[stumptoon]

i have a yamaha 70beto that is on a 24ft pontoon it is the original motor that came on it. It idles fine runs up to 5500 rpm on muffs in gear but in the water it wont go above 4200rpm. it all started last year when there was water in the one tank

have done:
new plugs
new gas/tank/line/pump/filter
carbs are clean no gunk

top cylinder runs leaner (white plug) bottom 2 are golden
havent checked compression this year but last year they were all equal dont remember the number

 

[racerone]

But on the trailer in gear is still neutral !!----The prop does not do any work.-----Check for spark on the top cylinder.----And yes check the compression again.