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Water in oil 350 5.7 OMC 800 I/O 1982+

M

madfish

New member
1979 20’ Tiara cuddy cabin
1979 OMC 800 Series stern drive
New engine about 4 or 5 years old 350 5.7 Chevy 260 hp
The whole stern drive has been replaced with an OMC 800 series (1982 +), after hitting a sand bar and braking the old stern drive. While replacing the stern dive (did it myself) I only removed the risers from the engine did not touch anything else on the engine. After putting the boat back together I took it for a test ride. When returning from the test ride I removed the engine cover and noticed milky muck on top of the carbonator that came from the hose of the valve cover. Of course water is getting in the oil. The engine is running great. I have replaced the oil and filter 5 or 6 times. I removed the intake manifold and see no indications of water leak. Removed the heads and had them tested the showed no defects. The cylinders showed no rust or water. Had the risers and exhaust manifolds tested with one exhaust manifold showing a leak. I replaced all gaskets for heads, risers, exhaust manifolds and intake manifolds. Also, put all NEW risers and exhaust manifolds on. I am still getting water in oil (milky oil coming up to the rockers) and the engine runs great. Have recently performed compression check and that shows all cylinders have a compression of @ 120. I have not had the intake manifold tested or replaced.
Did a pressure check in all cylinders as recommended by a friend. Removed plugs and applied air pressure to cylinders and check for bubbles in the area of thermostat hole with thermostat housing removed. No indication of bubbles in any cylinders.
Would you have any suggestions of where the water could be coming from or what I can check next?
 
You have a crack in the water jacket somewhere no doubt about it.

Where ? Valley between the heads, cylinder wall maybe.

Good news any 5.7 long block off a truck will replace the one you have before 89'.

You won't have to change anything on the block just use marine gaskets for the mani's risers etc no need to change the cam the engine mounted water pump take off your old block, starter, alt. carb and fuel pump, and dist. they are all maine i assume. Use the mani;s and risers that you have off the cracked block motor.

Remove the wires from the engine and they should just match right back up to the replacement block.

should be able to get a good block for under 1000 here in nj 800 with perfect compression junk yards are brimming with them now here.

Sorry it's the way i see it.
 
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put 15 psi air in @ green arrow
block hoses @ red X's with 5/8" bolts or dowel and hose clamps
the problem is where you hear the hissing
searay.jpg
 
gonna cost more to magna flux to find the leak. Try hy's methid first.

You will hear it. But you did everything right to this point same as i would have done.

This new motor was a crate motor or a rebuilt over bored motor ? See alot of rebuilders overbore way to mush.

30 over is all i would ever go never more. But they go 40-50 see the rings and all are easy to get.

Really want to find it for your own knowledge when you tear it down without the magna flux cost look close with a magnifying glass at the walls. Old days sleave it maybe.

In the air force we had experts on our own time we would sneak into the barn with motors and he would do the do every kind of welding chit you can imagine, for a case of beer or a ride in a plane that a Chief of the month won. Let the guy take the ride.

We did the base commanders jag he did a radiator flush never put in the coolant and blew a hole in the wall that was a byatch getting parts for, never a jag again. I happened to be his Chief there was perks but then there was heartache also. Plane had to be perfect.
 
The story was stupid of me to post i just should have posted the sleave stuff and the mag na flux.

Just trying to save you money.

Keep us informed. You did not reply about the motor was it a crate or rebuild ?
 
Possible intake manifold.

Remove the thermostat housing, get a long 3/8 socket extension and a small hammer. Place the 3/8 extension vertically in the hole where the thermostat housing was. Place it against the bottom of the manifold and push it with your hand. if it does not go through, tap it slightly with a small hammer. if the manifold is bad the extension will go through with very little effort.
 
Not with a new 5 years ago will the extension push thru, thats why i asked about what was new.

Try it anyway. Try everything and anything i say before pulling the motor.

Dockside is one of the best mechanical minds on here.
 
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I tryed the extension thing and the intake is solid. I tryed the air pressure, I hear no hissing or whisle. I had no gage to check the pressure, but I blew a whole in the water pump hose. Is there anything else I can test? Someone said to loosen the exhost manifolds and run water through the system and see if water comes out of the manifold joints. I am gain for anything before I replace it.
Air-in-engine1.jpg
 
the exhaust manifolds would be the next suspect. Running water in with them off is a good start as was suggested. Just slide them back on the studs. Riser to manifold gaskets are often the culprit...and it looks like those *might* be GLM manifolds which are notorious for having uneven mating surfaces there.

How much milk is the engine making? not just condensation is it?
 
A lot, I have flushed the oil 6 times. I have removed valve cover and run the engine and see gray to milky oil pumping through the rods. I will try the exhaust manifold test. The problem was before replacing exhaust manifolds and risers.
 
funny you didn't hear a hiss.
maybe instead of listening for a hiss, you could use a leakdown tester to see if the cooling system holds air pressure - 15 psi max. in there. don't put air in there without regulating the pressure.
 
If you have GLM exhaust manifolds and risers, your best bet would be to remove them and replace them with Osco or Barr. I have seen nothing but problems with GLM or HGE manifolds and risers.
 
i like osco and barr also. But all of them you have to check them that they are true.

Metal angle iron. They might just have a rough mating surface.

Still don't think it's that but like i said....... try anything and everything before you pull the motor.

You did drain the block and man's before the air test didn't you ?
 
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