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 ????

 

[Chris1956]

Gee, clean and rebuild the carbs, rebuild the waterpump, change the thermostats, bore out the bad cylinder and install a new piston. Say $500 plus 20 hours of your time, vs the cost of a new engine, is something to contemplate.

 

[JDusza]

Thanks for the encouragement. This would be a great project.
My driveway is already full. lol
J

 

[Chris1956]

It is probably the last chance to teach your kid how to rebuild an engine, as that motor is quite simple and easy to work on. Of course, that implies the kid is interested.

Off subject- when my kid was raving about a new video game, I asked him if he would rather play it or design it? I would have chosen the latter. He looked at me like I was stupid. Why would he want to design it?