Water in Oil MCM165 Mercruiser

[bdacjl]

Have 1984 MCM165 Mercruiser I/O. Did tuneup to find water in oil after running for a short period of time. Removed head gasket had a small suspect area but nothing conclusive. Turned over with plugs out and had water coming out of cylinder four. I think it may be the head gasket but just cannot be sure. Cylinder walls look OK.. Where else to Look?? Has water to water heat exchanger. Intake side of head seems to have rust in it?? Any way to check block with heads and intakes off without having to take it out??

 

[Lyle29464]

Re: Water in Oil MCM165 Mercruiser

you work too fast. You have went pass the point where it is easy to trouble shoot. I would take the head to a shop.

 

[bdacjl]

Re: Water in Oil MCM165 Mercruiser

It is there now.. going to have it checked and reworked... initial review does not indicate problems but they are going to clean, pressure test, valve job and resurface. Before I removed it Tested cooling system with 16-17 lbs pressure and it held. Just researching for areas to look at while I have it open before I reinstall if it isn't the head or head gasket.

 

[Lyle29464]

Re: Water in Oil MCM165 Mercruiser

sounds like all that is left is the riser.

 

[Don S]

Re: Water in Oil MCM165 Mercruiser

Cam seal is a common problem for the 470's, it allows coolant into the crankcase.

 

[bdacjl]

Re: Water in Oil MCM165 Mercruiser

Thanks for the input... Worked on the project a little more last night. Sorry but I am a rookie... can you explain riser more?? Drained the oil and it had allot of water... probably up to a gallon or so.. and this only after running on water hose for 10-15 minutes. One puzzling thing is I am not seeming to loose that much engine cooling water. This engine has a closed loop fresh water system through the engine and a heat exchanger that circulates lake water and goes out exhaust. Initial inspection on intake and exhaust manifolds looks decent. I cannot find an obvious area that this is happening. Also has obvious corrosion in piston four cylinder, water is getting on top of this piston no doubt. It is a 165 four cylinder. Keep the info coming.. it is a great help. I assume only way to rule out cam shaft bearing is total tear down??

 

[stonyloam]

Re: Water in Oil MCM165 Mercruiser

OK first things first. To check your cam seals: look at the front of the engine and you will see the engine water circulating pump housing. Look down on the lower starboard side of the pump housing. You will see a small weep hole. Take a toothpick or something and poke it in the hole to make sure that the hole is clear. Start the engine and look to see if any coolant is coming out while the engine is running. If not, then your seals are probably OK. Question: Did you have antifreeze in the block all winter? If not it can freeze. As for the riser, if you have a leak in the riser it can leak into the cylinder via the exhaust valves, especially #4. As for your head gasket, a blown #4 is quite common with this engine. Is it water or antifreeze in the engine?

 

[Lyle29464]

Re: Water in Oil MCM165 Mercruiser

He says it held 17 lbs. Unless he has an oil cooler I still think the riser is the next thing to look at.

 

[bdacjl]

Re: Water in Oil MCM165 Mercruiser

Antifreeze was in the unit... was not loosing engine coolant so I am suspecting the riser... cannot get back to check it until Monday but the more I learn the more it looks like the riser... #4 has obvious buildup so I know water was getting in on top of the piston. Thanks again.. I will update you when I inspect the riser

 

[bdacjl]

Re: Water in Oil MCM165 Mercruiser

OK back to r&d on the problem.. I have the exhaust manifold and riser off and an extensive visual inspection provides nothing obvious.... Can anyone tell me how to determine if the manifold and riser are OK.. testing procedures or what defect I am looking for. Remember I am getting lake water in on cylinder #4. Pressured antifreeze side and held so looking at cooling lake water side.

 

[nola mike]

Re: Water in Oil MCM165 Mercruiser

Lake water and not coolant into #4 certainly sounds like the riser or riser gasket. I just ran into a similar problem: http://forums.iboats.com/showthread.php?t=464427

 

[bdacjl]

Re: Water in Oil MCM165 Mercruiser

head checked out OK... valves reworked and head surface ground ready to go back on. Exhaust manifold seems to be the most likely candidate at this time. Obvious corosion on surface where it ataches to riser. Any ideas on how to determine if the exhaust manifold is bad?? How do you test it??

 

[Lyle29464]

Re: Water in Oil MCM165 Mercruiser

your early pressure test ruled out the manifold.

 

[bdacjl]

Re: Water in Oil MCM165 Mercruiser

would'nt that be true for the engine cooling loop only?? It is a closed loop with antifreeze and all. I am thinking this water is on the lake cooling water side. Not sure how the lake water travels through the exhaust manifold. I was not loosing engine coolant that I could tell and the water in the cylinder seemed to be lake water.. no green

 

[Bt Doctur]

Re: Water in Oil MCM165 Mercruiser

lake water does not go thru the manifold A/F does. water goes thru the heat exchanger and directly out the riser.

 

[achris]

Re: Water in Oil MCM165 Mercruiser

See below a water flow diagram. The item people are referring to as a 'riser' is the exhaust elbow. As it's a 1984 model the elbow and reservoir may be integrated and at the back of the manifold.

If you have water on the top of the piston, and it's not engine coolant (you're not losing any) then it can only from the exhaust elbow. You need to remove it and look very carefully INSIDE the elbow for a point where the walls have corroded and are allowing water to come back into the manifold. I usually take to them with a large screwdriver. I flip it upside down on a sturdy bench and hit the inside of the exhaust passage hard with the screwdriver. If I can punch a hole in the exhaust passage (into the water jacket) then it needed replacing anyway.

 

[bdacjl]

Re: Water in Oil MCM165 Mercruiser

Ok this is getting a little frustrating... I wish something would just show up broke. The riser is a water resevoir and exhaust elbow combined. I closed off the holes and filled the resevoir.. left it sitting for hour or so.. no water in exhaust chamber. Turned it over filled the laket water side untill it started coming out of ports in lower elbow where it injects into exhaust... no water shower up in upper chamber. Scrapped aggressivly with screw driver, seems solid. I cannot find the smoking gun.
Here is what I know... I had water blowing out cylinder #4 with plug out and I have lots of water in my oil when I drained it. By the way how do I get all that water / oil out of the oil pan before I start going back together?? Hindsite is always 20/20 and I wish I would have done more listening before I tore it down so I could have done more test, but when you have water coming out a spark plug hole and water in the oil it pretty obvous it has to come apart. So couple questions, any way to pressure test the block with heads and manifolds off and does anyone have a 1,2,3 checklist for me at the stage I am at?? Head checked out good, had pressure tested, reworked valves and ground surface. ready to go back on. It was not the head.

 

[stonyloam]

Re: Water in Oil MCM165 Mercruiser

Drained the oil and it had allot of water... probably up to a gallon or so.. and this only after running on water hose for 10-15 minutes.

A little more info here please. You drained the oil and it had a gallon of, water or of milky oil? If you had a gallon of water in addition to the oil, you would have had 2 gallons of fluid in there. There should be about 5 quarts of oil in there to start with.

 

[bdacjl]

Re: Water in Oil MCM165 Mercruiser

Water / Oil mixture.. looked like a chocolate milk shake... filled up almost half of a five gallon bucket... I would say it was probably two gallons.