Water in oil

[Kjohnson88]

New boat owner here. Purchased a 1999 Wellcraft 186ss with a 4.3 Mercruiser in August last year. We got to get out about 4 or 5 times to finish the season. I took it to a shop to get winterized and the mechanic let us know that he found water in the oil(milky), how much and how it got there is unknown.

I'm unable to post my SN of the engine because I'm deployed in the sandbox. Ill be returning to the states in about a month and want to start investigating.

Now my question is can an engine run perfectly fine with a cracked block, head/ head gasket or exhaust manifolds? It ran like a gem and never overheated(170 then the thermostat kicked on) Most of the time we made just short trips to anchor up and relax and to reposition to reanchor. I've read the water in oil thread in the adults only section. Just need some direction to troubleshoot.

Thanks

 

[Kjohnson88]

Re: Water in oil

The more I think about it the more I feel like the shop is trying to get more business out of me. They were a sketchy little shop that mainly worked on automobiles.

 

[hannez82]

Re: Water in oil

I'm sorry to say that it can run just fine, at least for a while, depending on where and how big a crack is. If I were you I would test to change oil a couple of times and see what happen. If it gets very milky fast then most likely you have a problem.

Good luck

 

[tazrig]

Re: Water in oil

:welcome: First off you really don't want a car guy working on your boat. They just don't have the experience that a good boat mechanic would have. To answer your question about a cracked block. Your engine would run with one but only for a very short period of time. A bad head gasket maybe a little longer but not by much. If it is one of those things it most likely happened on your last day out. When you get back post your serial number so we know exactly which motor you have. I noticed you said you just took short trips. If you don't run the boat long enough with each use you don't burn off the condensation that collects in the oil pan and that can give you milky looking oil too. If the oil was overfilled it will get all frothy and also resemble milky oil. You need to find out if the oil level was way high. If not You most likely don't have a cracked block. When you get back you can change the oil, note the level, run the engine and see if the oil level goes up. Hopefully it won't. If you have a fresh water cooled engine you can pressure test it to see if the block is intact. Here is a link to a bunch of Mercruiser stuff including service and parts manuals. It will at least give you some stuff to read up on until you get back to us with the serial number. One last thought. Check under your oil fill cap to see if you have kind of a gooky milky oil film on it. That's also a sign it could just be condensation that hasn't burned off from just taking real short trips. Either way if the oil is milky it needs to be changed out. Marine grade oil is designed to mix with water if you have infiltration but it won't give you the protection you need. By the way, Thank you for your service!

http://forums.iboats.com/mercruiser...cellaneous-mercruiser-information-329915.html

 

[Kjohnson88]

Re: Water in oil

I'm sorry to say that it can run just fine, at least for a while, depending on where and how big a crack is. If I were you I would test to change oil a couple of times and see what happen. If it gets very milky fast then most likely you have a problem.

Good luck

When I get back ill check the oil and run it. What constitutes "very milky"and "very fast"? How long should it be ran and how often should the oil be checked?

I seriously can't imagine that type of damage to an engine running perfectly fine and only operated under cruising speeds for 4-5 mins at most.

 

[tazrig]

Re: Water in oil

When I get back ill check the oil and run it. What constitutes "very milky"and "very fast"? How long should it be ran and how often should the oil be checked?

I seriously can't imagine that type of damage to an engine running perfectly fine and only operated under cruising speeds for 4-5 mins at most.

If you were only running it for 4-5 minutes at a time and then letting it sit that wouldn't be long enough to burn off the condensation. Unless your oil level is now way over the full mark on the dipstick the milky oil is almost certainly coming from just un-burned off condensation in the oil pan. It needs to be changed but doesn't sound like you have any worries. Change the oil, run it for a couple of minutes and check oil level. if O.k. Go for 5 minutes and check if O.k. then go 15-20 minutes. Keep in mind you may see a little milky oil because you won't get all of it out with the first oil change but it is the oil level you are checking. If the oil is just a little milky (chocolate milk color) you're O.K. If its white milky you need to change it again. Take the boat out and run it for a good 30-60 mnutes at planing speed and you should burn off most if not all of the water in the oil.

 

[Kjohnson88]

Re: Water in oil

If you were only running it for 4-5 minutes at a time and then letting it sit that wouldn't be long enough to burn off the condensation. Unless your oil level is now way over the full mark on the dipstick the milky oil is almost certainly coming from just un-burned off condensation in the oil pan. It needs to be changed but doesn't sound like you have any worries. Change the oil, run it for a couple of minutes and check oil level. if O.k. Go for 5 minutes and check if O.k. then go 15-20 minutes. Keep in mind you may see a little milky oil because you won't get all of it out with the first oil change but it is the oil level you are checking. If the oil is just a little milky (chocolate milk color) you're O.K. If its white milky you need to change it again. Take the boat out and run it for a good 30-60 mnutes at planing speed and you should burn off most if not all of the water in the oil.

Ah perfect! This is kind of a relief. The guy I bought it from is another military member and he might have over filled the oil. He is a crew chief after all so I can't put anything passed him.

 

[achris]

Re: Water in oil

Even a raw water engine can be pressure tested in-situ. Remove the 2 hoses going to the exhaust manifolds and plug them. Remove the hose going to the thermostat housing and use that to pressure up the block/heads...

That is the only conclusive way to determine if you have a crack somewhere.

Chris.......

 

[Kjohnson88]

Re: Water in oil

Even a raw water engine can be pressure tested in-situ. Remove the 2 hoses going to the exhaust manifolds and plug them. Remove the hose going to the thermostat housing and use that to pressure up the block/heads...

That is the only conclusive way to determine if you have a crack somewhere.

Chris.......

Thanks for the reply. Just to clarify, I'd remove the hoses from the thermostat housing leading to the exhaust manifolds and plug it at the housing. What is the best way to plug it? Then remove the hose from the thermostat coming from the water intake and test it from there. How would I seal the gap between the air pump and housing? Sorry I've never pressure/vac tested anything before.

 

[NHGuy]

Re: Water in oil

Get some hose blocking line clamps. Use them to close off the outgoing water lines that run to the exhaust.
Make up a plug to put into the line that goes into the thermostat housing. I used a rubber plug, drilled it and put a tire valve in it.
Pressurize it there with 15 or 20 psi.
Listen and watch for leaks.

 

[cecho]

Re: Water in oil

I've seen one engine with a bad head gasket that allowed water into the oil, one with a bad manifold gasket that allowed water into the oil, and one with a cracked block that allowed water into the oil. The one with the cracked block gushed water and oil everywhere. Total mess. The one with the bad head gasket also overfilled, but no where near as fast. The one with the bad manifold gasket was the slowest of all and experienced no poor running issues. It just turned the oil milky over the course of 10 minutes at idle and only at idle. The one with the cracked block was not my engine so I did not repair it. Once the repair of the other two engines were complete it took an oil change PLUS running it up to temperature to completely get all the water out. After the first oil change the water was still a little milky in both cases. It took a good 30 minutes to get all the water out of the oil. The oil actually ended up looking brand new once it did as well.


By the way, which lake(s) do you go to? I frequent Cheney and El Dorado myself.

 

[Kjohnson88]

Re: Water in oil

@ cecho
When I get back, I'll be checking things out and probably end up reviving this thread.

I've been to both. Cheney once to test run the boat before purchase and been to El Dorado a hand full of times to finish off the season. Cheney was just too low for me to feel comfortable. Also El Dorado seemed to have better scenary.

 

[cecho]

Re: Water in oil

I look forward to when Cheney becomes usable again. Right now it's too low to safely get a boat into it. I prefer Cheney for both fishing and water sports. El Dorado is a lot prettier, but all the trees normally hidden under the water's surface (currently visible) worry me. Now would be a great time to visit El Dorado to learn where NOT to go when the water's back up to where it belongs.

Good luck!