95 mercruiser 4.3 water in oil

[Rinker95]

I was just given a boat in an appropriately winterized state (plugs out of exhaust manifolds and block (2), return hose to water pump disconnected at pump). It started easily and ran fine with outdrive in a bucket. Ran it up to operating temp on land several times. Oil after that was good and looked new. Then I launched it, ran it 1/2 mile (good power.). Then I checked the oil: chocolate shake and overfilled (emptied 7 quarts). So far I have changed oil and filter, pressurized the engine side of the seawater cooling system: it held 15 psi and very slowly leaked down but still had some pressure an hour later. I didn't hear any air escaping anywhere. I have checked cylinder compression and it is uniformly 175 except 155 on #1. I have noticed that the exhaust bellows is loose from the outdrive side and the gearshift bellows is shot. I am new to I/O's and new to this forum. I have read the forum a lot so far and appreciate the wealth of information and experience here. I am wondering how to logically approach this motor issue at this point.

 

[alldodge]

You have a crack, just need to figure out where. Running on a hose doesn't have the same pressure or volume. Could be the intake or block, might be the exhaust and with compression at 175, check to see if there is water in there

 

[Rinker95]

Thanks for the reply, AllDodge. A couple things I left out. The plugs were all the same, a little sooty. No evidence of water on any plug. No hint of hydrolock. No water coming out of cylinders while cranking with all plugs out. Shouldn't the air pressure test of the engine cooling have ruled out block, head, or intake cracks or leaking gaskets? Guess I don't understand that test. How should I go about checking to see if there is water in the exhaust? Remove riser? manifold?

Thanks

 

[alldodge]

Only going by what your saying. Mentioned it held 15 psi and leaked down slowly. The leak can be from a bad connection, or could also be from a crack. Running on a hose does not produce the same water flow, and more importantly the same amount of heat. The extra heat expands things and a leak can increase to show what your seeing.

There is only two ways for water to get inside the block, a crack or bad gasket

 

[Scott06]

Take off the intake manifold look for rot under thermostat and cracks in block just below cylinder head.

 

[Rinker95]

Thanks very much AllDodge and Scott06. I will go ahead and take off the intake manifold and get back to you. From previous posts of others, I thought that pressurizing the engine water system would produce more obvious (audible) results if positive.

 

[Rick Stephens]

I doubt your problem is exhaust related. That doesn't occur often in the quantities from use, but from running and then stopping. Any cracks in the exhaust manifolds, the subsequent water ingress happens slowly, first into the cylinders and then down to the oil pan by seeping past the rings.

Your situation really is striking that in use it filled the crankcase with water, fairly short use at that. Most likely, there is a crack. Most common place for a 4.3L (or any SBC) is in the gallery right above the lifters. This is a thin spot that only takes a little freeze and it cracks. So when you pull your intake, check it out and check carefully above the lifters running lengthwise.

That much water, sorry to say, you have a crack.

 

[Rinker95]

Thanks very much Rick. I really appreciate the experience you guys have and your willingness to share it. Amazing.