johnson 15 hp fourstroke dies out on full revs

[yojo]

i have a 15 hp 4stroke johnson engine . the engine starts and revs to full throttle when out of water when i put on d boat and run it under load at full throttle it dies out it will run on half throttle all day. i had it at johnson main dealer they said they cured it but was exactly the same when i got it home 3 times this happened [ help help]

 

[racerone]

Stop winding the motor up to full throttle out of the water !!----------------Bad, bad practice.----------------Try priming the bulb at fulll throttle to see if it is a " lack of fuel issue "---------Could be water in the fuel.------------------If fuel is left to sit in these carburetors for long periods of time they tend to plug up.---------Always run carburetor dry when done.------------------------I would give the carburetor a thorough cleaning ( take it apart ) and blow out all the small passage ways.

 

[yojo]

new petrol , carburetor cleaned, bulb pumped, mecanic cant find prob will have to scrap it . thanks for your help[ racerone ]

 

[racerone]

Maybe it is running on one cylinder only.--------No such thing as a motor like that that needs to be scrapped.

 

[haffiman37]

Hook the fuel hose directly at the carb and use primer bulb as pump.
If working, a fuel pump issue.

 

[Boobie]

Do a cyl drop test on it and see which cyl is not firing.