MJ's Blown Piston

macojoe · #1 06-01-2006, 07:15 PM

Ok just for kicks, I took the head off today, here is what I found

Also something you can't see, there is a small hairline crack in the bad sleve of the middle piston.

msbhammer · #2 06-01-2006, 08:34 PM

OUCH ! :-/ :'( :'( :'(

Vic · #3 06-01-2006, 09:26 PM

Oh man sorry to see that MJ. I'm sure you'll have her going in no time.

macojoe · #4 06-01-2006, 10:07 PM

shes done Vic!! I have not the time or cash or no how to repair!!

I am looking to get a motor from Blue-Runner now.

bigshrimpin · #5 06-01-2006, 10:45 PM

MJ - That doesn't look bad at all from the pics. Take a shot of the hairline crack in the cylinder wall for me . . . I've never seen one of those before. There's some nice aluminum skuff and maybe a little scoring from the ring in the middle one?? Can you catch your finger nail on the groove?

macojoe · #6 06-01-2006, 11:00 PM

yea I can catch my nail easy.

I tryed to get that crack to show, its way in when the piston is in. I will try again tomorrow.

Skools Out · #7 06-02-2006, 12:04 AM

yeah that one would need a boring. then see if it's a threw crack if no use it and bore the rest.

Blue_Runner · #8 06-02-2006, 01:56 AM

I must say I was expecting to see something God aweful, but it doesn't look terrifying in the pic. I'm sure the old digi-cam probably can only do it about 30% justice compared to the naked eye though.

Crack kills.

76GMC1500 · #9 06-02-2006, 03:57 AM

That's a microseizure tansitioning to a full on seizure. *The metal on the cylinder is obviously aluminum from the piston being transferred to the cylinder wall. *Microseizures are generally caused by lack of lubrication, but can be caused by overheating. *Overheating localized to one cylinder is caused by lean fuel/air ratios, detonation, and advanced ignition timing. *This is a carbureted motor where oil is mixed in the carb? *I will say that the problem was caused by the carubretor. *If you do plan to reuse these carbs, REBUILD the one from the bad cylinder and have the others checked out before installing them on a new motor or you could end up in the same position.

Now, you want to get back on the water for cheap? *You have here what is a mostly good motor short of one cylinder and one carburetor. *How mechanically inclined are you? *You could strip the motor down to a bare block and take the block to the best machine shop in town. *You will get the best rates at an automotive machine shop, the process is the same regardless of application. *Any hotrod shop that deals with newer engines will be the best. *To sleeve a cast iron engine block, parts and labor come to $90 per cylinder. *Of course, your engine being an aluminum cast in liner engine can add some complicatoin and can add a little to the price of labor and the liner cost is going to be sky high. *If the liner is thick enough, they can just bore inside of the liner and install a sleeve just like on an iron block. *If the liner is thin, they have to bore the old liner completely out and start from scratch. *This is a little more costly. *For the best deal on a replacement piston, go to Wiseco. *They make drop in replacement pistons for a lot of engines. *If the failure is lubrication related, *you may want to replace the adjacent main bearings and connecting rod big end bearing. *You will certainly want to replace the connecting rod small end bearing as there is a good chance it was overheated. *Your wrist pin will probably come out blue and gold from the heat.

On further examination, I take back what I say about lubrication related. *That is definately an overheat failure. *Lubrication microseizures take place low in the cylinder where the piston skirt transmitts connecting rod thrust to the side of the cylinder. *The majority of the material is located at the top of the cylinder where the piston shouldn't make contact with the cylinder wall. *What appears to have happend to me is that your piston ring failed (causing the low compression readings you got earlier in the season). *The failed piston ring allowed combustion gasses to blow past the piston and heat it up to the point of seizure. *I feel confident in telling you that your ring failed because if it were still intact, it would have scuffed much of the aluminum deposits off of the cylinder wall.

#10 06-02-2006, 10:41 AM

Hi MJ,

It has been a long time since I last posted but I feel that you need some encouragement with this. As you will remeber I blew my 175 Merc a couple of seasons ago and was really bummed out. But, all has turned out ok.

Get the manufactures manual and a lot of plastic baggies for parts, pull the power head and take it down the basement. Tear that sucker down to the block. It's a 2 cycle- hardly any parts at all! Get it to a machine shop and get an estimate- might not be too bad!

I did it with my engine. No experience necessary. Did mine in just a few nights.

Go for it! What do you have to lose?

Go for it