Water in Oil - Resolved!

[Chris224]

I figured I'd add to the knowledge base of this forum with an actual solution as opposed to those posts looking for help but then never say what the issue actually was or how it was resolved.

I bought my 2004 Mobius LSV in late 2020. It was past the end of season, so I brought the boat home and winterized it. I ran the boat in my driveway with a fake-a-lake. In spring I went to de-winterize and found my oil appeared milky.

I inspected my exhaust manifolds and noted water visible in the exhaust ports. I figured that the manifolds/riser must have failed and replaced them. I again ran the boat in the driveway with the fake a lake and found there was still water getting into my oil. Water flow from the exhaust/muffler looked good, and temp and oil pressure were fine. Boat ran well. I was a bit stumped.

Further research showed that the intake manifold gaskets were problematic on these motors, so then replaced these. Again ran the boat in the driveway several times letting the engine get up to temp. This time I found even more water in my oil. The block showed no signs of freeze damage/cracking, so I removed the heads, however the head gaskets looked fine. I found that my lowest cylinders were quite full of water however were near top of their stroke and again the exhaust ports and exhaust manifolds were full of water.

I noted that my driveway slopes somewhat downward, and the angle of the engine with the V-drive also causes the bow facing end of the motor to point downward. These angles combined with a 3/4" high cast iron dam in the risers was enough to cause water to back up in the risers and flow back into the motor through the exhaust.

Lesson learned: Only run your boat on land if level or bow high. My slight to moderately sloped driveway was enough to cause water to back flow into the motor and fill cylinders with water. My engine suffered seemingly no lasting damage as I was monitoring oil level and condition, but I'm out many hours of labor and stress as well as some parts cost.

Since running the boat in the lake where the stern sits lower, or on land with the bow level or slightly elevated my oil is clear and clean. $1500 in parts, 6 oil changes, and a lot of stress: issue resolved.

Hopefully this helps someone. Remember the simple stuff.

[SONIC]

Ouch that's a rough lesson to learn!

I always try to keep the boat running as much as possible if I'm on the hose, I don't like to let the hose run without the boat on for this reason.
I like to start and stop the boat and the hose at the same time if possible as there's always an open exhaust valve.

[jzelt]

Thanks for this. I went from plunger fake lake to putting the hose in a bucket, fill it and run ~1" hose to the v-drive. I figure this also gives me accurate reading on the impeller capability, makes sure the plunger doesn't fall off while I am in the boat and no one is monitoring, etc. I always run mine with slight bow decline in the driveway, but fortunately haven't had the same result.