1992 johnson gt200

[rb215]

Help needed I have a 1992 johnson gt200 on a 20 ft nitro Motor is bogging bad when I try to get on plane hit’s 3000 rpms and set there until I play with trim finally gets on plane but will only turn 5000 rpm on top end.The boat used to have a great hole shot and would run around 70 mph according to past owner witch is a friend so I believe him boat sat for three years before I got it. Ok now for things that have been replaced stator timmer base three coils plugs water pump carbs cleaned vro disconnected running premix 50/1 had compression checked 75 psi on all 6 cylinder Still stalling at full throttle trying to get on plane Have read on about ever boat form there is found about 5 people with same problem but no tells what fixed the problem I hope someone can help with this

 

[racerone]

Do a test for spark.-----Sounds like it is running on 5 of the six cylinders.----And perhaps use a strong flashlight to look into the carburetor bores to compare how fuel comes up the main nozzles.

 

[rb215]

we did the spark test had three weak coils replaced them checked all coil again spark was 7/16 like manual says
Thanks so much for your reply

 

[racerone]

Have a shop look into possible issues with crankcase compression.

 

[rb215]

Can you tell me what crankcase compression will cause

 

[racerone]

Your motor has 6 separate crankcases.-------There are sealing rings on the crankshaft.-----There have been issues with these sealing rings.-------Compression would leak from one cylinder to the next resulting in performance issues.-----I can't help you other than suggesting where to look.-----Seems you have looked all over the ignition and carburetors already.----The 75 PSI compression in cylinders would also be a concern to me.----Perhaps pull one cylinder head as a new head gasket is cheap.