Merc 470 Water in oil

[btaylor507]

Hi all, I have a 4cyl Merc 470 165 Hp in a 1989 Regal Sebring. I'm getting water in my oil at a rapid rate. This motor has a closed circuit cooling for salt water. I've heard it could be a cracked block or head and the thing is that I lose no coolant. Anitfreeze is always full. Its the fresh water coming in or from the heat exchanger correct? I have no clue where to start and any info would be greatly appreciated. I have rebuilt a few Evinrude outboards so I might be able to tackle this one. Thanks guys!

 

[stonyloam]

Re: Merc 470 Water in oil

Are you sure it is fresh water and not antifreeze? The only place fresh water comes in contact with the engine is the riser, and it would not leak in while running. How much is coming in?

 

[stonyloam]

Re: Merc 470 Water in oil

Time for a compression check and a cooling system pressure test. Autozone will loan you the tools to do both (free). Good luck.

 

[btaylor507]

Re: Merc 470 Water in oil

Thanks for the quick reply, much appreciated. When I purchased the boat the guy ran it for about 10 sec in the driveway to show it runs. Ran great. When I got it home I put on the earmuffs and ran it for about 20 secs then shut it off. I then checked all the fluid levels and the antifreeze was topped off, bright green. When I checked the oil I noticed it was VERY milky and up past the full mark on the dipstick. I called a Marina the next morning and they mentioned that it could have gotten water in the bilge and leaked in past the rear main seals. So I borrowed a oil pump and pumped all the oil out and filled with new. Then started and ran it for about a 30 secs then it stalled. I then checked the oil again and there was water/oil mix (light grey/tan color) all the way up the dipstick. A lot of water got in a very short period of time. So I checked the antifreeze and it was still full and didn't go down a drop. This is for sure a close cooling system with a 4" heat exchanger. I know what you mean by the fresh water getting in when it shouldn't come in contact with the motor at all. The only thing I can think of is a cracked exhaust manifold but I was told that if it was in fact that, that the cyl would fill with water and wouldn't run at all. And even if the cyl filled with water that the seal between the rings wouldn't allow that much water get in. It would more likely burn off. Im baffled. Its also sad too cause the 2 year loan I took out to by this only has one payment left and I still haven't even got it on the water yet lol. Any help, advice, diagrams etc would be GREATLY appreciated. Im ordering the service manual for the outdrive and engine tonight. Maybe I can trace the freshwater path and see where it could possibly be leaking. Thank you so much guys!

 

[stonyloam]

Re: Merc 470 Water in oil

Something is very wrong here. The seawater path is pretty simple. In from the impeller, through the voltage regulator, into the heat exchanger (front), out of the exchanger (rear), through the PS cooler (if you have one) up to the manifold and out the exhaust. There is no way that the water can enter the engine from the manifold while it is running. The exhaust gasses will simply not allow it. Can you smell antifreeze in the oil? It does not take much water to turn oil milky. Did you change the filter? If you drain out the oil, it should be about 5 quarts. The only way I can see for this to happen is a bad head gasket or cracked head. A cracked block is possible, but not likely. A compression test, even cold will tell a lot. Good luck.