1999 Johnson 15 overheat - now won’t rev full and loss of power

[TurnerBFC]

I’ll try to keep it short for you guys, trying to figure out what happened. Motor somehow over heated when my buddy took it to the local store on the water and we towed it back, let it cool, and then fired it up. I verified water was coming out of the tube by the back so I knew there was water flow. Took out the thermostat to ensure it wasn’t stuck, etc and it seems to be functioning correctly. I changed the plugs here a week later and the boat seems to have a loss of power and doesn’t seem to rev to full throttle.

I’m wondering if the overheat could have messed up some gaskets in the carb or if we just shaved a good chunk of life off the motor and it needs a set of pistons now.

Looking for any insight anyone has or any similar problem someone may have had!

Thanks guys!

 

[racerone]

Perhaps it picked up a plastic bag and that blocked water flow !!----A compression test is the next thing to do.----I often say install a new impeller every 5 years.------The common reply today is , no my motor is cooling just fine.----Then one day the motor goes ''''BOOM " and if pistons are damaged and you can do the repairs yourself OK.----If you have to pay a shop you might just as well get another motor.

 

[TurnerBFC]

Perhaps it picked up a plastic bag and that blocked water flow !!----A compression test is the next thing to do.----I often say install a new impeller every 5 years.------The common reply today is , no my motor is cooling just fine.----Then one day the motor goes ''''BOOM " and if pistons are damaged and you can do the repairs yourself OK.----If you have to pay a shop you might just as well get another motor.

Thanks for the quick reply! I’ve rebuilt many Seadoo engines and currently working on my Bowrider so I’m confident I can tackle this. Do you know what the compression should be on it?

 

[kbait]

Is it running on one cylinder? Cd boxes can fail with excess heat, and can fail for just one cylinder. If compression tests good (90+ psi and even between cyl’s), check spark w/gap tester or perform a cylinder drop test. Good luck!

 

[TurnerBFC]

Is it running on one cylinder? Cd boxes can fail with excess heat, and can fail for just one cylinder. If compression tests good (90+ psi and even between cyl’s), check spark w/gap tester or perform a cylinder drop test. Good luck!

It’s definitely running on two cylinders, but I won’t throw out your suggestion. I’ll dig into this. I just have to get my compression tester this week and bring it back up to the cottage where the boat is.