Can’t get up to rpms which makes my boat go 15mph

[Djohnson86]

I can’t get my 1986 ranger with a Johnson gt150 v6 above 3000 rpms and 15 mph will under a load I have done a compression test 5 cylinders at 90 and one at 86.I have checked the plugs with a spark light and all came back good.Went through all fuel lines and cleaned carbs run through sea foam in the gas. I marked the prop and it slipped maybe a half inch what else should I check I have run out of options

 

[racerone]

Another Ranger with 150 HP and problems.----How did it run last year ?----Did the problem show up suddenly ?-----Checked the flywheel key ?----Compression is low.----Perhaps test with another gauge.----Or remove bypass covers to inspect pistons rings , 6 screws each cover and a $2.00 gasket.