Water in oil

[z-drives]

I'm stumped, and frustrated, so here we go....maybe someone here has an idea.

​Generic marine power 5.7 pre vortec, fresh water cooled hooked up to an alpha drive.

A few weeks ago it strarted running like crap after a day of fishing, barely idling. Figured it was the carb, so I'd look at it in a few days. Get back and for the fun of it pulled the dipstick and yep, gunk in the oil (water). Not good, but seeing as the engine had a good amount of hours on it I decided not to totally mess with it and just drop in a new engine, NOT REBUILT. Had a new engine delivered, swapped over all accessories (thoroughly cleaned) and was up and running. Ran awesome in the driveway, and when first in the water. took it easy and ran to the marina a few miles away.

Now back at marina, i see some steam coming from the breathers in valve cover...further inspection shows........WATER in the XXXXXXX oil again. I can't say definitively its antifreeze OR seawater from the oil cooler (didn't use the same oil cooler, used a spare to try and rule that out).

This leaves me with the possibilities of:

-intake manifold which i re-used; cleaned the hell out of it and did not see anything to be concerned about as in cracks etc
-oil cooler
-head gaskets on a brand new engine
-block on a brand new engine
-something I am not thinking of

Basically back to where i started. what the *&%^&@#


MOD EDIT - Hold off on the cursing.

 

[Bt Doctur]

usually the steam indicates a broken exaust valve spring allowing water to enter the cylinder. being a "new" motor anything is possible.
having an oil; cooler shall we assume its an inboard?

 

[z-drives]

Its technically an I/O with an alpha drive, but a jackshaft configuration so the engine is foward of the transom assembly. Weird to have the same problem again; different cause, same cause, who knows.Intake manifold is the only thing in common but i THINK if there were a problem there I would have seen it. I pulled the intake tonight and gaskets looked they were on there fine, i had a tough time lifting the intake off the engine.

 

[NHGuy]

I think your intake manifold has a center passage to carry heat to the choke stove coil. Seems to me that's an exhaust passage, but if I'm wrong it could carry cooling water. Test if for leaks.
Also test the oil and/or power steering cooler. A new engine should not do what your's did. I'd guess you have a cooler internal failure. If it's that save the motor you pulled out and use it or sell it.
To test the engine cooling system put the intake manifold back on and let the seals set. Block the engine cooling system exits with line clamps and add air at the hose to the thermostat. You will need to make up something to hold 12 or 15 psi. Once the motor cooling system is pressurized listen at the carburetor, exhaust and valve covers for hissing. While doing this turn the motor over about 1/4 turn of the crank at a time to actuate different valves.
Actually you could include the oil cooler and PS cooler in this loop too. Add pressure at the cooler entry instead of at the thermostat. That would be the least amount of work, Although you'd need to be a contortionist to get the cooling water line off the inner transom tube with a standard Alpha. Maybe you could reach your jackshaft water entry a little easier. If it's too much trouble to reach you could get a piece of heater hose to connect up to the coolers.

 

[Scott Danforth]

how tall are the risers? if your motor sits low and you have the 3" stock risers, you may need to increase riser height.

 

[z-drives]

the risers are about a foot above deck level. The boats about 30 years old and these aren't original parts but the setup has been time-tested. I'm leaning towards intake or oil cooler. I'll probably bypass the oil cooler to rule that out (dual filter setup so i'm not terribly concerned about oil temperature) and as its the only thing from the old engine i'll get a new intake--i have wanted to anyways. The more i've read it seems common enough for them to leake on these chevy's. The middle passage on this one is exhaust, but its plated-off on the top.

the raw water intake is through a through-hull and strainer to a engine mounted raw water pump; its all 1-1/4" inch and pumps a ton of water. the outdrive impeller pump just goes overboard at the transom.

If i had the time I'd go pull that cooler today and pressure test it. I'll pressure test the coolant once the new intake is on.

 

[300sflyer]

Are you using the original exhaust manifolds and risers?

 

[z-drives]

Are you using the original exhaust manifolds and risers?

yes, but fully inspected when i swapped the engine. they're only a few years old with good gaskets/stainless block off plate; only riser has raw water in it manifolds are engine coolant.