Mercruiser 165 oil in water

[50170]

Bought my first boat and found a milkshake in the oil pan. I removed and plugged the water line into the manifold, and pressurized the block through the water inlet to 12 psi. I had a few leaky hoses, but it only dropped a few psi in 1/2 hour. No other sounds. Block looks solid under the manifold. I am going to plug the exhaust boot and fill the system with water tonight. What else can it be and is there a better test.

 

[Don S]

Re: Mercruiser 165 oil in water

How much water are we talking about?
When you did your pressure test,did you drain the cooling system first?

 

[50170]

Re: Mercruiser 165 oil in water

I am guessing a quart to quart and a half. Cooling system was drained and so is the oil pan. Trying to get as much out as possible. Previous owner won't share any info with me. I did not pressure test the manifold though.

 

[50170]

Re: Mercruiser 165 oil in water

Pressurized the system and water filled the cylinders. Found intake manifold to be cracked. Block is solid.

 

[NHGuy]

Re: Mercruiser 165 oil in water

So it seems that the water went in that way before and eventually got by the rings. Treat it by getting some oil on the cylinder walls right off. I'd say to remove the spark plugs, ground the coil or if you have a safety lanyard just disconnect it there, squirt some oil in the plug holes, change the milkshake to oil and crank the motor to distribute the oil.
If you want to be really fussy and perfect you can put some water to the lower unit so the impeller doesn't get spun dry, but then you ought to pull a hose off the cooling system inside so it doesn't re water the combustion chambers through the intake crack. With that little cranking it's probably unnecessary though.

BTW good for you if all you need is an intake manifold! Well maybe good for you, is your motor the inline 6, with the combination manifold?
I hear they can run into some money.

 

[50170]

Re: Mercruiser 165 oil in water

Yeah it's the inline 6. I ended up taking off the head to view the cylinder walls and inspect for cracks. I dumped some marvels in each cylinder, but am going to roll the engine by hand to check the deck height of each cylinder. If it is just the manifold and head gasket it will be over 700