3 Litres of water in my sump!

secarter23

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Mar 5, 2018
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Hi Guys,

New to the forum, and I have what I think is a pretty interesting issue, that I cannot find anything at all anywhere on the net about! Engine is 3.0 Mercruiser, Alpha 1 in a 1991 Sea Ray 170 Bow Rider

Boat was running perfectly, it suddenly made a clunk then went into neutral then stalled under low revs. I waited for the engine to cool down, checked the oil, visually checked what I could and everything seemed fine, oil level was perfect, nothing milky from the filler cap. Could not get it back into gear no matter what I tried so waited for a tow. I got towed back from the bow with everything turned off.

Got to shore, started engine, still not forward or reverse just a loose throttle, there was a low pitch whirring from the stern drive so I turned the engine off, trailored it then drove home. Its a 3 hours drive through steep uphills and downhills. Did not check anything else after this point.
Took the boat to my marine mech and they got the alpha drive going back into gear said it was a sticky selector and that was sorted. They then did a check over everything, only to find roughly 3L of clean water sitting under clean (not milky) oil in the sump.

No one could figure this out, every mech I speak to says if there was 3L of water sitting in the sump the oil would be 100% milky if the engine had've been running while water was in there. Yet, theres not an obvious passage for that amount of water to enter the engine? Not that I can think of or see from my research and knowledge.

Exhaust manifold and riser seem to be fine, compression is 140 icyl 1,2,3 and 100 in #4, so theres an issue there but surely 3L cannot make its way down the cylinder past the rings unmixed. So I think I have to rule out the manifolds. There was no water sitting in the head or in the exhaust manifold when removed

I guess my question is, after being towed, could enough water end up in my exhaust, then find its way into the engine somehow driving up and down hills for 3 hours? And if so where could that happen. My trailor is a nightmare to get the boat high enough on and the winch cant pull the full weight so I need to try 3 or 4 attempts in deep water to get the bow high up front. Maybe water creeps in while thats going on?

Its a very strange situation for us, but maybe someone out there has seen something similar before? Any help at all would be greatly appreciated!
As for the back #4 cyl, I plan on doing an engine swap over winter, however want to sell this current 3.0 merc, running but as is, currently the engine runs like a dream. Would love to sort this out, get it in the water for the rest of the summer then swap it out for an LS1 over winter.
 

Bondo

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There was no water sitting in the head or in the exhaust manifold when removed

Ayuh,...... Welcome Aboard,...... Was there any little rust tracks in the black carbon areas of the manifold or head exhaust ports,..??

Does it, or did it freeze where you live, 'tween when it quit, 'n now,..??

If water did slip past the rings from the exhaust, it would be clear water, under clear oil,.....
 

secarter23

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Mar 5, 2018
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Hi Bondo thanks for the reply!

I had used it a few times already before this trip and everything was fine after inspecting, so no to the freezing in between, im in new zealand, so still warm here this time of year.

As for rust marks we found a couple of smaller rust marks on the #4 cyl end on the exhaust port (gasket side), but nothing inside the port obviously, then a rust mark near the same point on the head but it never got passed the head gasket. If that makes sense? All gaskets seemed to be fine when we removed them all. Water pump needs replacing but its leaking externally so I cant see that being an issue, just a loss of cooling pressure I guess?
 

Rick Stephens

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Aug 13, 2013
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6,118
I can see overflowing the exhaust into the cylinders while attempting to load with the stern pushed too deep. Even the exhaust shutter will only help slow a surge like when the engine quits while underway, not a constant underwater stern low condition. Water will make it through the rings unmixed if the engine isn't running. Only thing that will mix the water would be running with it half full of water. I bought a boat with a new engine in it that the previous owner left out with a tarp over the engine bay but no flash arrestor protecting the carburetor top. The motor had a lot more than 3 liters of water in it just from dripping off the tarp into the carb. (ended up rebuilding the new motor)
 

secarter23

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Mar 5, 2018
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Thanks for the reply Rick!

Yeah that would make a lot more sense if it came from loading onto the trailor as I never started the engine after loading the boat and then the drive back could have forced more water into the cylinders, possibly a worn piston ring in #4 cylinder might be letting more through than the others. I might just have to put it down to something like that, as weve had it running again now and no water in the oil at all on muffs which cancels out any block issues. Runs mint too

Will just have to check the sump after each outing for water. As mentioned earlier it only needs to last until end of summer (2x more trips) then ill head down the LS1 swap route.

Thanks guys!
 

Bondo

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Apr 17, 2002
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Ayuh,..... You should probably pull #4 plug, 'n turn it over on the starter, as soon as it's on the wagon, on level ground,.....

Then put the muffs on it, 'n start it, as soon as possible to completely dry out that cylinder,....

No reason to cause more rust in there, than there already appears to be,.....
 

secarter23

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Mar 5, 2018
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Hey so for anyone wondering, we think we have found the only way this could have happened. Checked the exhaust flapper, no flappers attached at all, gone! Replaced that.
So we think there must have been a fair bit of water pushed up there with the engine off one way or another. Then the drive back on the trailor up and down steep hills has allowed water into engine the engine via the exhaust manifold.

Could be wrong be that seems the only logical explanation for that amount of water. Hopefully a one off! Will find out this weekend after some boating!

Thanks everyone
 
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