Cracked Cylinder Block? Pictures, What do you think?

[harrylarson]

Hello, I am planning on rebuilding '78,150 hp, Johnson. #3 piston and cylinder are scored, I have opened up the crank case and found what might be a crack in the cylinder head for #3, see pics. I also included a picture of the cylinder block for #5 to compare. I'm not sure if this is a crack or just a small flaw in casting, should I continue with the rebuild with this cylinder block, or is this a deal breaker? What do you think?

 

[oldcatamount]

Re: Cracked Cylinder Block? Pictures, What do you think?

I'd say it's a flaw in the casting judging from the pictures. It seems like the metal is to thick to crack like that.

 

[emdsapmgr]

Re: Cracked Cylinder Block? Pictures, What do you think?

You may not mean that the head was cracked. Looks like it's the block casting. That engine uses the old spaghetti (rubber string) type seal. As long as that specific grooved surface and mating flat surface is ok, you should be able to rebuild the engine and have it run ok. The damaged spot is just to the side of this critical area and probably won't hurt/affect anything. I would probably reseal the replacement spaghetti seal with the newer factory type gel seal (used in later crankcases) -as extra precaution.

 

[ENSIGN]

Re: Cracked Cylinder Block? Pictures, What do you think?

The gel seal addition is a good idea,you're only sealing this area aganist air leaks.

 

[halfmoa]

Re: Cracked Cylinder Block? Pictures, What do you think?

Hello, I am planning on rebuilding '78,150 hp, Johnson. #3 piston and cylinder are scored, I have opened up the crank case and found what might be a crack in the cylinder head for #3, see pics. I also included a picture of the cylinder block for #5 to compare. I'm not sure if this is a crack or just a small flaw in casting, should I continue with the rebuild with this cylinder block, or is this a deal breaker? What do you think?

Get the block to a magnaflux testing facility or order a non-destructive penetrant kit. You can find them around the 80 dollar range (not magnaflux brand) and I'm betting you'll get your money out of it...especially when you start renting it out lol.

 

[harrylarson]

Re: Cracked Cylinder Block? Pictures, What do you think?

Yes I meant cylinder block not cylinder head. I didn't think this would an issue but just needed some confirmation before I moved on. Thanks, everyone.