Needing help/ 4.3 mercusier

[mlcooley89]

Hey guys, I bought a 88 searay with a 4.3 mercusier. When I bought it the ppl told me it just needed exhaust manifolds. Well we bought new one's and we changed the oil cause there was some water in it the oil. And we did a compression test on the engine and all cylinders had 150 to 160 psi and held. So we replaced all spark plugs and changed the gas and put everything back on and started it. It runs good and sounds amazing. But it started to let a milky(oil and water) substance come out of the breather tube. So I shut the engine off and haven't started it since. I was told it could be cause it has water in the engine cause if the manifolds and just need to change the oil like 4 times. But also heard it can be a cracked block. But if it was a cracked blocked would it still have all compisson in every cylinder or would it not hold compression??

 

[dubs283]

A cracked block due to freeze damage, corrosion, etc can still run perfectly with good compression

Best way to find out if the cooling system is sound would be to drain and pressure test it. Should hold 15 psi indefinitely, if not you need to locate the source of the leak

 

[mlcooley89]

Yeah, and that's what I'm afraid of. And how would you do that?

 

[Scott Danforth]

Yeah, and that's what I'm afraid of. And how would you do that?

Drain the block

Take the hose from the transom shield and tee it off with the 2 hoses going to the manifolds. Pressure the block and heads to 15 psi of air. It should hold forever.

If it doesn't hold pressure, listen for the hissing