Water in oil - almost there
 

Ok, I edited out most of the rambling detail now that I've gotten some sleep. :D

I've been battling a minor water-in-the-oil issue. Skipping all the rambling detail, what I now know is that water is introduced to the #8 exhaust manifold port after the t-stat opens. I've ruled out the Stainless Marine exhaust through running it wet, dry, half wet, pressure tests etc.

It's only enough to milk up the oil a little bit, not make oil, at least not enough to detect on a dipstick. Keeping the idle up keeps the water mostly blown out but at idle as in testing in the muffs at idle, it's enough to soak the inside of the #8 manifold port blowing it out.

When running hard then coming to an idle, it'll sometimes drop a cylinder if I don't' idle it up, and idling it up will clear it up so I suspect it's a full flow of water after getting pretty hot and enough that it's killing the number 8 cylinder if I let it idle down then making me believe it may be related to the head gasket.

From the exhaust side of the valve (when the manifold was off), the valve and port look normal, not like I'd expect to see valve and port if it's moving a lot of water. And the motor still runs strong after 140 hours and this it's 5th season yet it's been doing this since day 1 so like I said, it's not much water, but enough to be noticeable and a concern.

Any ideas? The motor is a mild 540 with iron GM heads.

I know the head will be coming off at least, but I'm looking for ideas that might put me at ease until then since we're using the boat more this year and I'd hate to have it out of commission in the middle of the season.

That sucks Jim,I'm sure you will get it figured out -missed you at Table Rock....

It does suck. It's not bad enough to destroy anything but enough to make itself known and taunt me.

BTW, who is The.Savant? :drink: Obviously we know each other and enough to make you post for the first time in 4 years. :evilb:

You should leak test #8. A tweaked exhaust valve will suck water back.

I think I've got that ruled out. After running it for just a few seconds after I could feel the t-stat opened and pulling the riser and the #8 port had water obviously blown up and out but not enough to get to to the rest of manifold yet, and from the top out through the riser was bone dry. If I didn't run it long enough for the t-stat to open it was dry as a bone in the manifold.

But thanks for the suggestion and keep'm coming. :drink:

Hi SeaRay Jim,

There's a good article on water in oil here:

http://www.boatfix.com/merc/Bullet/01/01_13.pdf

Helped me a lot in grinding through the various possibilities. It takes you step by step in determining the possible cause.

Best of luck