Mercruiser 3.0 - Water in Oil After Overheat

[CableGuy1978]

Hello,

I have run this engine for a few year now with no problems with the engine itself. I have changed the oil regularly, and have never seen any signs of water in the oil or on the under side of the filler cap. When I got it, the guy had changed out the Mercruiser manifold and replaced it with an OMC one as he said it had cracked and let water into the cylinders. The motor has always ran great with NO water leaks. The rig up job the guy did to get the exhaust elbow to connect with the exhaust tube in the transom is quite a site too, but I have never had a problem with it, no leaks anywhere.

My impeller gave up on me a few weeks ago and it over heated. I pulled the outdrive and replaced the entire impeller and housing assembly. The old one had what looked like blisters in the plastic housing from excessive heat. Engine cooling restored and was the best I have seen after water pump replacement. Engine starts fine idles normally and runs as good as it always has for me.

The rig up job with different plumbing boots and clamps that join the exhaust riser to the transom had melted some and now some water and exhaust leaks into bilge. Nothing too serious as the bilge pump pumps it out. But now it seems as though the engine compartment under dog house is relatively damp as condensation is forming on the thermostat housing where the fresh water is pumped up from outdrive.

Another check of the oil filler cap showed signs of water since overheat. Dipstick was clean, with no evidence of water. Close inspection of engine after a cold start up shows water leaking from somewhere under manifold and running down side of the block. Also gasket at the exhaust elbow on top of the manifold is showing a small amount of water.

So I am thinking that the manifold gasket is in need of replacement. Could this be the cause for water getting into the oil? Otherwise I am suspecting the head gasket as I would have originally especially after an overheat. Is there a method for pressure testing an engine the same as you would for an outdrive?

Any ideas would be greatly appreciated.

Also shortly after that, I ended up with a leak from what I am guessing is the U-joint bellows which left the boat on bottom, fortunately the water was shallow enough around the dock that it only submerged the starter and alternator, and never reached the oil dipstick, but did cover the oil drain tube. Oil level never changed, but water is evident in the crankcase. I am assuming that water must have leaked through the cap in the oil drain tube.

At this point, I have pretty much given up on this boat for the season and am focusing on next season. Once I get the gasket leak dealt with, and replace the oil, what is the process for getting the remaining water out of the engine? I can change the oil and filter a few times. Will the remaining water "burn" off through running the engine and getting things warm after a few oil changes?

Thanks for taking the time to read through this and offering any ideas!

 

[86 century]

Re: Mercruiser 3.0 - Water in Oil After Overheat

I would error on the side of caution if you pull the manifold the head is just a few more bolts and a cheep gasket. That I am aware of a manifold leak will not get to the oil so you probably took out the head gasket with the over heat. It will not cost that much to know for sure.
Good Luck

 

[coheej]

Re: Mercruiser 3.0 - Water in Oil After Overheat

I would do a leak down test, trying to see if one cylinder showed problems. If you find a bad cylinder, you will then have to determine if it's a head gasket or a cracked head or block. The leak down test is usually done with the piston at top dead center; if you done see any problems you might back the rocker arms off and do the leak down at bottom dead center to check cylinder walls for a crack.

 

[cr2k]

Re: Mercruiser 3.0 - Water in Oil After Overheat

Not to mention you are going to need a starter very soon.

 

[CableGuy1978]

Re: Mercruiser 3.0 - Water in Oil After Overheat

Thank you for the fast responses! That was pretty much what I was thinking as far as head gasket. I am thinking on replacing the manifold anyway with a mercruiser one so that everything lines up properly, so I wasn't too concerned with replacing that gasket as it would get done then. My main concern is to get the water out of the engine asap. I would like to winterize at this point and get all of the small problems ironed out over the winter.

What should I do with this engine at this point before winterizing? I'm trying to avoid spending a lot of cash this late in the season, as I planned on changing the manifold during the off season. However, if it must be done then I will do it. I am hoping to find a place where I can store the engine in a heated shop where it will stay above freezing, but I'm not banking on that at all. Is it possible to fill the engine with antifreeze while things like the manifold and such are removed?

As for the starter, yep its a lot less than perfect since it was submerged, but I can deal with that over the winter as well.

Thanks again for the info!

 

[BAproject]

Re: Mercruiser 3.0 - Water in Oil After Overheat

How much water is in the oil? The first thing I would do is drain that oil and get it out of the pan! Take a look and see how much water is in there.
I would also recommend pulling the plugs and squirting some mystery oil in each cylinder to break down any rust that may have built up.
I'm not sure if the exhaust manifolds are new or not, but a crack on the inside of one of those manifolds could be responsible for water getting into the engine, if the exhaust valve is open when he engine is shut down (where the crack might be) then it will leak right in.
Not sure the gasket would cause this problem unless its so bad in the bilge that water is splashing up and dripping in through a bad seal.
From what I have read it is rather unusual that the head gasket just goes south. Do a leak-down test to confirm before you think about pulling the heads.
The other thing to check is your bellows (not exhaust), if there is a tear in any of the boots water can back-flush right into the engine.
You need to fix before winterizing or you will be replacing your engine next year instead of doing the proper maintenance this year!

 

[CableGuy1978]

Re: Mercruiser 3.0 - Water in Oil After Overheat

I'm guessing the manifold (OMC) happened to be one that they guy who suckered me into buying this boat, happened to have laying around and was a quick replacement for the cracked mercruiser one originally on the engine. If it is still serviceable then I will keep it as a backup as I want to replace it for a mercruiser one so that my exhaust riser lines up properly with the exhaust tube on the transom. But, that old OMC manifold has never given me any trouble that I know of.

After the overheat, the most evident place to find water was under the oil fill cap and it was visible as milky coating inside. The pan itself shows little evidence of water, and since my u-joint bellows leak ordeal, there appears to be some water in the oil, but not enough to turn the oil milky in the pan. My problem is that both things happened so close together that I'm not sure if water ran in when it half-sunk, or if there is a gasket failure somewhere.

If there happens to be a problem with the manifold gasket leaking, would there be a problem with leaving the manifold off for the winter providing I protected the exposed intake and exhaust openings from stuff getting in there?

On a side note... One positive thing about being suckered with this cursed boat is that it has given me ample opportunity to learn volumes about this engine and outdrive. Everytime I have learned to fix one thing, something else would go. It sure gives a great sense of pride when you are riding around in a boat that didn't even have the engine or outdrive on it a few hours earlier, and to know you did it yourself. Things become very evident, like how quick this boat was pieced together to make it work long enough to sell it, and how easy it is for a marine shop to rip customers off who don't have any idea what's really going on. The next time I buy a boat like this, I will definitely be prepared, and will at least have a more educated eye for things. There is no substitute for experience.

Thanks again