[tuff82]

Hey just built a 454 marine engine for a jet boat, the engine is cooled by water coming out of the jet drive, after about 1/2 hour of running, the oil on the dipsitck came out milky, the level did not go up tho????, just wondering if anyone has come across cracked blocks and possibly places to look for cracks in the block, thanks!

[oldschool hero]

To check for a cracked block you will have to tear it down and magnaflux test it. First thing I would is perform a compression check on each cylinder to see if it may be a blown head gasket.

[tuff82]

Right, while the engine is together right now, I might try pressuring the cooling system and locating the leak maybee something simple

[oldbogie]

Originally Posted by tuff82

Hey just built a 454 marine engine for a jet boat, the engine is cooled by water coming out of the jet drive, after about 1/2 hour of running, the oil on the dipsitck came out milky, the level did not go up tho????, just wondering if anyone has come across cracked blocks and possibly places to look for cracks in the block, thanks!

Could be a small leak or just condensation, boat motors tend to run pretty cool to where there isn't enough heat in the oil to drive out the normal waters that comes as a by product of combustion in the blow-by.

A pressure test of cooling jackets could find a leak there, most often those type leaks are gaskets but sometimes casting cracks as well.

Bogie

[tuff82]

Yeah I tested it tonight and the cooling system is ok there are no leaks, buy I do have a faulty intake restrictor valve thats letting full pressure and volume of water to my block and causing my water injected headers to come on at idle, causing inversion to my cyls, blowing by the pistons