johnson 90hp 1991 piston #2/cilinder seizure

[Fisherman1010]

Goodmorning mecanics,

the motor died on me last time during a wot run. I had this before, that it died on me during a wot run, but i cld always fire it up afterwards, but not this time.
Thinking back for the previous times it died, it always ran again, and at home i always performed a compression test to see whether it was a seizure or not, and the compression tests always turned out in specs
Well this evening it died and wld not fire up again, well sort off, and i had to put my boat on an anker for the night.

Getting the boat home i did the comp test, and cilinder 2 had just 40psi, so ok, bad cilinder.
Thinking back, all the times it died at wot, it were mild seizures:facepalm:

Well, i want to clean this baby up.
But need to know what caused this overheating problem.
Thermostat not working properly? Water blokkage some where? Bad impeller? Why did the alarm not go off and put the motor in slow mode?

Anyway, i know you guys have lots of experience and hope wld guide me a little around.
First of: do i need to split the motor from the transom/gear case?
The cilinder has aluminium buildup from the piston, i maybe can clean that we acid, right?

So, why did this cilinder go, without the alarm warning me? Why cilinder 2 and not with cilinder1?

Here is a pic.

 

[Haffiman]

Re: johnson 90hp 1991 piston #2/cilinder seizure

To me it looks like you have been running with 'water injection' from a bad head gasket???
Uoy will need to remove the powerhead from the leg and strip it completely down. I'm afraid you'll find piston in cyl#1 ready for a change as well.
Clean out water passages with Salt Away, and at the same time replace the deflectors.

 

[Haffiman]

Re: johnson 90hp 1991 piston #2/cilinder seizure

To me it looks like you have been running with 'water injection' from a bad head gasket???
Uoy will need to remove the powerhead from the leg and strip it completely down. I'm afraid you'll find piston in cyl#1 ready for a change as well.
Clean out water passages with Salt Away, and at the same time replace the deflectors.

 

[Fisherman1010]

Re: johnson 90hp 1991 piston #2/cilinder seizure

Hi Haffiman, we meet again
You helped me last time with some comments on the top bearing. I replaced it, but like you said, it did not need to. I tried to solve the freeplay at the flywheel.
Hmmm water injection....that wld explain the plug color. I will post a pic of them.
Ok so i will start getting the powerhead of the leg.
Will post pictures along the way.

O btw haffiman, with water leakage, wld the comp test show 125psi? This particular cilinder showed 115psi before she died.