1986 E70TLCDC Piston Destruction - What Causes This?

[JDusza]

Hi.
1986 Evinrude E70TLCDC, G1114897.
No compression in the top cylinder.
Opened it up and this is what I find.
The piston is eroded right down to the ring.
Any idea what causes this kind of damage?
By the looks, I'd say it has been naughty for quite some time.
Thank you,
J

 

[racerone]

Broken piston ring.----Overheating.----Ignition too far advanced.-----Water pump tell tale not changed to come off top of block per service bulletin in 1994?----Wrong prop?----Poor quality oil.-----Water pump impeller not changed every 5 years.

 

[Chris1956]

How about running lean?

 

[Mc Tool]

Detonation ,its only done one cylinder , mostly adjacent to the exhaust port , which can rule out a few things. Poss lean running on that cylinder

 

[racerone]

Forgot to mention a partially plugged carburetor.----At any rate if you rebuild it ,you do need to determine the cause.----If not it will fail again.

 

[JDusza]

I'm not sure we'll rebuild. Exactly for that reason. We don't know what caused it.
Thank you to all.
J

 

[racerone]

Time for a big $$$$ 4 stroke with a computer ????