water in engine oil

[Ike-110722]

Checked my engine today for the first time since I put the boat in the water at the beginning of June. The oil is milky. Obviously water is getting in somewhere. Did not have this problem last year or at the beginning of this year. The engine is a Mercruiser 165 (GM 250) in line six. It is 42 years old. The only thing on the engine that hasn't been replaced is the block (and internals) and the head. It is raw water cooled. No heat exchanger. All new exhaust manifold and exhaust/cooling system parts. All bellows and gaskets on sterndrive and so on. It is only used in fresh water. And, the engine runs very well. Reaches max rpm at WOT and does 30-35 mph.

Anyway here is my plan.

remove old oil and replace.
replace oil filter.
remove plugs one at a time, look for water, and crank to see if there is water in the cylinders.
check compression on each cylinder
run engine until it gets up to normal temp and run it for ten minutes or more.
drain and change oil and filter again
run engine
check oil for water.

I suspect a leaking head gasket (had that problem with another engine) but no white smoke in exhaust.

Worst scenario, cracked head or block.

Have I forgotten anything I should check or left out a step?
Any other suggestions, advice?

 

[alldodge]

Checked my engine today for the first time since I put the boat in the water at the beginning of June. The oil is milky. Obviously water is getting in somewhere. Did not have this problem last year or at the beginning of this year. The engine is a Mercruiser 165 (GM 250) in line six. It is 42 years old. The only thing on the engine that hasn't been replaced is the block (and internals) and the head. It is raw water cooled. No heat exchanger. All new exhaust manifold and exhaust/cooling system parts. All bellows and gaskets on sterndrive and so on. It is only used in fresh water. And, the engine runs very well. Reaches max rpm at WOT and does 30-35 mph.

Anyway here is my plan.

remove old oil and replace.
replace oil filter.
remove plugs one at a time, look for water, and crank to see if there is water in the cylinders.
check compression on each cylinder
run engine until it gets up to normal temp and run it for ten minutes or more.
drain and change oil and filter again
run engine
check oil for water.

I suspect a leaking head gasket (had that problem with another engine) but no white smoke in exhaust.

Worst scenario, cracked head or block.

Have I forgotten anything I should check or left out a step?
Any other suggestions, advice?

Could also be the exhaust manifold leaking water into the cylinder(s)

 

[abrx7]

That same thing happened to a friend of mine. In his case it was the thermostat being stuck open. Same exact motor too

 

[Ike-110722]

Thanks. I will spray some WD40 in there. Good idea.

I can't imagine how a stuck thermostat would allow water into the oil but I will check it. Now that I recall the last time I took it out it was running cool.

 

[Bondo]

Checked my engine today for the first time since I put the boat in the water at the beginning of June. The oil is milky. Obviously water is getting in somewhere. Did not have this problem last year or at the beginning of this year. The engine is a Mercruiser 165 (GM 250) in line six. It is 42 years old. The only thing on the engine that hasn't been replaced is the block (and internals) and the head. It is raw water cooled. No heat exchanger. All new exhaust manifold and exhaust/cooling system parts. All bellows and gaskets on sterndrive and so on. It is only used in fresh water. And, the engine runs very well. Reaches max rpm at WOT and does 30-35 mph.

Anyway here is my plan.

remove old oil and replace.
replace oil filter.
remove plugs one at a time, look for water, and crank to see if there is water in the cylinders.
check compression on each cylinder
run engine until it gets up to normal temp and run it for ten minutes or more.
drain and change oil and filter again
run engine
check oil for water.

I suspect a leaking head gasket (had that problem with another engine) but no white smoke in exhaust.

Worst scenario, cracked head or block.

Have I forgotten anything I should check or left out a step?
Any other suggestions, advice?

Ayuh,..... Doesn't Anybody check the fluid levels of their boat, Each, 'n Everyday at the 1st start of the day,..?? I do,.....

Where is/was the oil Level when ya checked it,..?? How far Over-full,..??

 

[Ike-110722]

Changed oil and filter. Ran engine for about 15 minutes.
Changed oil and filter again. Oil is still slightly milky but clear.
There is a small amount of water coming out of the manifold gasket just forward of the carb, right about where one of the bolts for the manifold is located. When the engine heats up the leak stops (at least on the outside). I checked the torque on the bolts and two were not as tight as the others. There are no other visual leaks. There is no water in the cylinders so I am now thinking (and hoping) it is just the manifold gasket

checked plugs and compression
cylinder
1 dry plug looks good 125#
2 dry looks good 120#
3 slight amount of oil, no water, 120#
4 slight amount of oil, no water, 120#
5 dry looks good 120#
6 dry looks good 120#

The engine runs well. However, it does not seem to be warming up to normal operating temps. I shot it with a infrared heat gun and temp was about 103 deg F, a lot cooler than it should be. I think the thermostat is stuck open.

 

[Ike-110722]

Turned out to be a leaky gasket between the Riser and the exhaust manifold. All fixed. Cost $306.50 almost all labor. The gasket was $3.46.

 

[Ike-110722]

Turned out to be a leaky gasket between the Riser and the exhaust manifold. All fixed. Cost $306.50 almost al labor. The gasket was $3.46.

 

[NHGuy]

:facepalm: oh man! Well at least your motor isn't toast.

 

[airshot]

Thanks for letting us know the solution to the problem...