Blown head gasket

[Tominator88]

What causes this center 2 cyl on each side I bought a boat with this engine knowing it was blown but I was considering using the vortec heads and Mercruiser intake on the other motor I have for boat

 

[Tominator88]

The engine still started and ran smooth only under a load it was knocking it’s a Mercruiser 357 alpha

 

[stresspoint]

coincidence .

good guess would be one side was already blown from age and the other followed shortly afterward

looks like the steamer hole was clogged on both sides with rust , this would have caused hot areas in turn heating the gaskets ,

hopefully there is not too much burn cut and the block and heads can be re used.

 

[Scott06]

First thing I would think it got overheated at some point. Would check the head and block surfaces for flatness. While the heads are off may have them gone through at a machine shop. Was compression good on the other cylinders?

would change out the impeller in drive as a precaution.

 

[Scott Danforth]

Detonation and overheat.

Looking at the pics, you may need a new block. It looks like there is some fire-slotting evidence

Step 1 is to clean the gasket surface and check the deck for flatness

 

[stresspoint]

Detonation and overheat.

i just took a better look at the pics , the steamer holes are blocked by the gasket that was moved over them my bad should ware glasses when looking at pics on a small laptop.

anyway that said , it has been hot , real hot at some point how it got so is the question.
Op needs to go over the entire cooling system and have the block hot tanked and crack tested if he is intending on reusing it, same with the heads .and intake manifold.

probably would not hurt to look at fuel quality and carb settings either looking at the rest of the cylinders.

 

[Tominator88]

Other 4 cylinders had good compression I have anouther freshly rebuilt non vortec 5.7 that I put in the boat Grady white 241 offshore and I am disappointed in the speed I never ran this boat with this motor I bought it broken I would like to take these heads to machine shop and do the vortec upgrade I’m not looking for a speed demon just would like to cruise at at least 25 without pushing my rpm’s too high

 

[Scott Danforth]

I’m not looking for a speed demon just would like to cruise at at least 25 without pushing my rpm’s too high

Build a stroker if you want to keep RPMs low. Or let the motor sing like it should

 

[tank1949]

Detonation and overheat.

Looking at the pics, you may need a new block. It looks like there is some fire-slotting evidence

Step 1 is to clean the gasket surface and check the deck for flatness

If salt used block, pitch it. Insides will be crap too. You may be able to salvage if fresh water used, but I wouldn't chance it.

 

[Lou C]

It would be interesting to see what the block looks like between those cyls after you get the gasket material cleaned off.

 

[ROY WILLIAMS]

The engine still started and ran smooth only under a load it was knocking it’s a Mercruiser 357 alpha

the engine block is the rusted it around the pistons rusted hole