1987 mercury 60 hp piston damage

[Jumbo3905]

Hello, I had a piston failure in my number 1 cylinder and I was wondering if anyone might be able to identify the root cause from seeing the piston. The engine did not seize but the metal pushed onto the plug shorted the spark killing the one cylinder. I recently had to replace the stator and timing trigger but the motor ran fine for a month before this occurred. From the picture can one tell if this was a progressive failure or does this type of failure happen quickly.
thanks for any help.

jumbo3905

 

[Faztbullet]

That be preignition from improper timing or bad bais in switchbox. When we raced Inlines we would jack timing to till we started getting erosion(throwoff) and then back it down a tad, plus we wuz running avgas

 

[Jumbo3905]

Thanks for the response, does this breakdown happen over time or does it happen pretty quickly

 

[racerone]

The top cylinder is known to have overheat issues.----You need to install a new water pump impeller every 2 years.

 

[Jumbo3905]

The top cylinder is known to have overheat issues.----You need to install a new water pump impeller every 2 years.

Even if the tell tale is showing a good flow of water out of it?

 

[Faztbullet]

"Thanks for the response, does this breakdown happen over time or does it happen pretty quickly"
If timing is a tad high it will happen slowly but gradually build up faster as the erosion takes place. A Racer said these do have a overheat problem but piston shows no other signs leading to a cooling problem, tis electrical.

 

[Jumbo3905]

Hello Faztbullet.....do you know if these piston pins are pressed fit , I assume they are by how tight they are. Any tricks to installing them easily.

 

[Faztbullet]

You have the new style ros so take it off crank and you can remove the circlips. and tap wrist pin out. New piston will come wit wrist pin. The new one will slip right in

 

[Jumbo3905]

You have the new style ros so take it off crank and you can remove the circlips. and tap wrist pin out. New piston will come wit wrist pin. The new one will slip right in

I removed one of the other pistons to inspect the needle bearings and now I'm trying to re-assemble it. The piston pin is very tight and I feel like I need to press it in. I tried with a small drill press but still very tough. Do you suppose I need to "de-burr" the piston around the circlip ring using a fine grit emery paper. I'm seeing the same thing on the piston that is bad as I'm using it as a test setup. Still waiting on the replacement Piston but I expect it this week. thanks.

 

[racerone]

Heat ( boiling water ) will expand the hole in the piston.----Putting pin in the fridge will shrink it a wee bit.------Might slide together.

 

[Jumbo3905]

Heat ( boiling water ) will expand the hole in the piston.----Putting pin in the fridge will shrink it a wee bit.------Might slide together.

It seems the piston pin holes on the piston is out of round (overheat or wear and tear..) if I can get the piston pin to go in is this ok to use or am I
looking at getting another replacement piston. Thanks

 

[Jumbo3905]

Does the piston pin have to be able to rotate in the piston itself or is it ok if only the needle bearings are able to rotate the piston