Mercruiser 5.7L Water / Condensation in Oil?

[sidebojj]

This question is for a friend of mine. He has just bought a 1983 Formula III Thunderbird with a 260hp Mercruiser 5.7L. He got the boat from a lady who won it in a divorce settlement and did not really know how to take care of it. She blew the outdrive on it and then it sat for a couple years. We replaced the outdrive with new and fired up the boat no problem. Motor runs very well idles smooth no miss, knock, vibration. Check the oil on the dipstick and it looks good. Before we took it out this weekend we changed the oil. As soon as the pump starting sucking the oil out we could tell there was a problem. The oil looked like Chocolate milk. At this point we thought it was done, but we got a few gallons of oil, filled it back up and ran it again for awhile. Oil still looked bad (which we expected because the pump doesnt get all the oil out). So we drained the oil again through the pan, and poured a few quarts of oil down the valve covers and let it run out the pan. We then filled it up with new oil again and ran it for another 20-30min. The oil again looked milky, but the oil level was not going up. (we still had not changed the filter, he only had one filter, stores were closed and he wanted to wait for the last oil change to change the filter). We drained the oil again. At this point after talking to a couple people who said they have seen condensation cause the oil to turn, he decided to take it out the next morning and keep and eye on the oil and see if the level went up. We wanted to get it hot and see if the internal leak showed up.

Well we took it out and the boat ran great, oil still looks like it is a bit milky but much better then before. Oil level did not go up at all. Had the boat out on the river all day Saturday and Sunday with no problems.

We were wondering if anyone here has had an experiance with a boat that has been sitting for a couple years getting enough condensation in the oil to turn the oil and cause it to contaminate the new oil? Is it possible we have a bunch of "sludge" in the bottom of the pan that is contaminating the new oil? I find it hard to believe he has a cracked block or head because the oil level never went up. Any other theories? How much water does it take to turn the oil milky?

Also is there a product you can run through the oiling system to break down this sludge if that is our problem?

Any thoughts would be appreciated.

 

[wire2]

Re: Mercruiser 5.7L Water / Condensation in Oil?

5% water will make oil quite milky looking. Did you happen to keep the oil you removed from the engine? Let it stand for 24 hours, then pour slowly into another container. The water will be at the bottom and you'll be able see how much was in there.
As the engine operates well under water boiling point, it will take many hours of running to get all the "milk" out of the oil.
Keep an eye on the valve cover vents to the flame arrester, that's where it will accumulate. You'll see a bit of vapor there while running.

 

[captdre]

Re: Mercruiser 5.7L Water / Condensation in Oil?

Could be sludge build up too, do an oil flush to get it out and refill with clean oil and new filter. They sell a cleaning product I cant remember what its called but its pretty common, just follow the directions.

 

[Acer2428]

Re: Mercruiser 5.7L Water / Condensation in Oil?

Keep in mind, my experience is with cars, not boats, BUT:

Replace your filter!

Now, after saying that, this sounds like a perfect time to pull the pan off the bottom and do a nice manual scraping of all the crap that's in there. Run oil through it with no pan to run some of the gunk out.

Then, do short changes. I use crappy Oriley's oil and and filters for this in old vehicles and change the oil 2-3 times in a 300 mile period. Does a good job at getting stuff out of the valleys where water can pool up.

 

[Haut Medoc]

Re: Mercruiser 5.7L Water / Condensation in Oil?

Have you pulled the plugs to look for any signs of water in the cylinders or rust on the plugs?.....
I must say that the fact you ran it for two days with no problems is encouraging though....​

 

[kbetts]

Re: Mercruiser 5.7L Water / Condensation in Oil?

Acer, It might be easy to pull the pan off a car motor, but it will not be easy to pull the pan off a boat motor while it is in the boat.

If it was mine, I would buy a few gallons of diesel fuel to wash out the motor. Fill it to full mark on dipstick, and run motor for a few minutes to flush while on muffs. Do this a couple of times. Let the engine drain through the oil plug, not by pumping it out with a pump. I would then change the filter and add fresh oil. Just keep an eye on it to make sure the oil is not getting above the full mark while running.

 

[sidebojj]

Re: Mercruiser 5.7L Water / Condensation in Oil?

We did not find any signs of water in the cylinders.

Filter was changed with the third oil change before we took it out and will likely be changed again before the boat goes back out on the water.

I had not heard of running diesel for oil in it. Works pretty good? Sounds like it would

We did not keep the oil we drained but will keep it when it gets changes again this week.

Thanks for all the suggestions, keep them coming

 

[Acer2428]

Re: Mercruiser 5.7L Water / Condensation in Oil?

I know, pulling the pan would probably require pulling the motor.

The diesel fuel trick works well for a little bit of water like you'd get in a car motor. Used it before, but it's hard on seals. Just don't run it for long.

 

[HT32BSX115]

Re: Mercruiser 5.7L Water / Condensation in Oil?

Don't run STRAIGHT diesel!
That will be a good way to spin a bearing. all you want to do is dilute the oil a bit.(I wouldn't do it at all.....but many have done it without damage I guess!)

Another way to clean it up would be to use oil like 5w-30 and put a 180-200 degree T-stat in it to get it to run a little hotter temporarily.

All you want to do is get it hot enough to evap the water out. You don't want to break loose ALL the crud too fast or you run the risk of plugging an oil passage and starving a bearing etc...


Regards,



Rick