Blowby through vent tube? Mercruiser 3.7

[Dubed]

I'm dumbfounded. Never seen anything like that. I saw the cylinders after machine work and before install and they looked beautiful. I just saw the motor, oil is perfect, head gasket is perfect, but those two cylonders show signs of heat damage. Shop owner has never seen this either. He is going to stand by it and help me out though. Looking for a new block or maybe re-sleeve

 

[alldodge]

Have not seen anything like that before. Shop owner is Aces

 

[76SeaRay]

Check the bore diameter. Did the block get over-bored, cylinder walls too thin and broke through? Piston slap caused a ring to gouge in? If over-bored too far, I wouldn't sleeve it. With that kind of a failure I would be looking for a replacement block.

 

[Dubed]

Have not seen anything like that before. Shop owner is Aces

Strange right?

 

[Dubed]

Check the bore diameter. Did the block get over-bored, cylinder walls too thin and broke through? Piston slap caused a ring to gouge in? If over-bored too far, I wouldn't sleeve it. With that kind of a failure I would be looking for a replacement block.

Just got a call and he found a block. Hopefully it's good

 

[Scott Danforth]

looks like the aluminum and ring material may have had condensation sitting on them and it could be galvanic corrosion in the one pic when you zoom in. I would trust a good metal sleeve, however a replacment block would be my recommendation.

 

[Rick Stephens]

I cannot imagine! Did the machine shop have any thoughts?

 

[nola mike]

So here's the damage. Very bizarre

Was that 2 cylinders?

 

[Dubed]

Was that 2 cylinders?

Yes #2 and #4

 

[Dubed]

I cannot imagine! Did the machine shop have any thoughts?

Crazy. They had no idea. They do tins of high performance marine engines and the owner has been there for 40 years.

 

[Scott06]

Crazy. They had no idea. They do tins of high performance marine engines and the owner has been there for 40 years.

It may be a moot point since they are honoring their work...

My thought is ring end gap or mismatch between ring/piston and bore
What did the rings and pistons look like from those cylinders?

 

[Dubed]

One quick question.
I'm getting a donor block for my 3.7 that the machine shop can bore to match and replace my failed block with. Will any 470 / 3.7 block work? I believe the blocks were all the same throughout production

 

[Scott Danforth]

One quick question.
I'm getting a donor block for my 3.7 that the machine shop can bore to match and replace my failed block with. Will any 470 / 3.7 block work? I believe the blocks were all the same throughout production

yes, the blocks are the same

 

[Dubed]

yes, the blocks are the same

Thank you