5.7 vortec overheated

[doubleb]

newbie here. i just bought a 2003 jetboat with only a hundred hours. the previous owner forgot to open the valve to let water in the engine. once overheated the idiot opened the valve and let the cold water in. it is a vortec 350 roller motor the only thing that makes it marine is the intake and exhaust and waterpump block off. the head gasket was blown apart by the steam i am guessing. I had the heads magnafluxed and decked just to make sure. they were fine. i am leary on the block. it looks fine, i see no cracks. the cylinders still have the factory swirl marks. it did push the freeze plug out though. could that have saved the block? were would this block crack if it were going to. any info would be apprieciated. p.s the oil looks super clean. there was a little milkiness in the lifter valley but i think that was from all the steam.

[tokymon]

most like to crack between the center cylinders they get the hottest

there is some products for checking this i dont know any off the top of my head right not though

[hog]

Ithought the marine Vortec 350's got different main bearing clearances?

peace
Hog

[doubleb]

I talked to indmar the people who put it together and they told me that they just buy crate engines and put there stuff on it

[hog]

I talked to indmar the people who put it together and they told me that they just buy crate engines and put there stuff on it

Nice, thanks for the info.

peace
hog

[THEFERMANATOR]

GM has a seperate engine division that handles marine engines. Most all of them since 97 are built off of the infamous 4 bolt main blocks that came in 96-00 3500 trucks. They only differences was that they used better head gaskets in them to resist rotting from saltwater, and a different camshaft along with some got a timing cover without a crank sensor hole in it. VOLVO would take them and put COMP roller rockers in the 320HP version they turned out, but other than that they are all pretty much GM inside.

[tokymon]

if youre build another boat engine. I would consider going to a closed engine cooling system with a heat exchanger, these system aren much better in that you dont have dirty water going though the block. I have seen more than 10 motors crack du to not flushing the sand and crap from dirty river water out of the block

[Supercharged111]

GM has a seperate engine division that handles marine engines. Most all of them since 97 are built off of the infamous 4 bolt main blocks that came in 96-00 3500 trucks.

What's infamous about the 4 bolt main block?

[stroker97k1500]

GM has a seperate engine division that handles marine engines. Most all of them since 97 are built off of the infamous 4 bolt main blocks that came in 96-00 3500 trucks. .

The Above is an incorrect statement.
The exact same GM 350 / l31 block that goes to Mercruiser, Volvo, and Indmar from GM built in Mexico, uses a 2 bolt main block.
The cam is different and the head gaskets internally use a stainless wire mesh material like said above.

However Volvo and Mercruiser are "forced" to purchase the marine intake manifold with the engine from gm but Indmar does not have to since they tune their engines specifically with different style intakes and exhaust and ecm tunes to make more and less powerful versions of the 350

The only part I am not exactly sure about is if they(GM) uses stronger valve springs in the marine 350 engine to handle the prolonged high rpm like 5 grand usage of where most people run those engines to reduce power loss and valve floating issues.

"Usually" when the marine motors overheat and then fresh cold water is pushed into the motor the heads and or deck surfaces will warp and crack b/w the inner 2 cylinders b/w the deck surface and the water passage area b/c it is pretty thin at that area on the heads.

[THEFERMANATOR]

I've got a 98 5.7L MERCRUISER Sitting outside that is in fact a 4 bolt main block, and I had an 04 MERCRUISER that IIRC was also a 4 bolt main block.