Water in bottom of exhaust manifold

[Zackman]

I have a 99 Mercrusier 350 Mag with 235 hours, which is used in fresh water (or at least as fresh as Louisiana river water can get).

I took the exhaust riser off to inspect them and the manifolds. The riser's and manifold's passage all looked really good with only slight rust scale and no signs of metal loss.

When I looked at the bottom on the exhaust manifold passage (looking down from above into the main gas passage) there was a slight amount of water just sitting there. I would guess a depth of a few thousands of an inch.

We have had warm days and cool nights lately with a lot of fog in the mornings. Could this water just be from condensation or is further investigation warranted?​

 

[Bondo]

Re: Water in bottom of exhaust manifold

We have had warm days and cool nights lately with a lot of fog in the mornings. Could this water just be from condensation

Ayuh,... That would be my WAGuess...

 

[Don S]

Re: Water in bottom of exhaust manifold

ALL Vortec engines have some reversion due to valve overlap. After idling for a while they will show a little water in manifolds, much like you describe just from the engine sucking moisture from the riser outlet back into the manifolds. It's normally not enough to cause a problem, but it can cause you to think there is something wrong.
One thing Merc does recommend, is that if you idle for any length of time, to rev the engine up above 1200 rpm for a few seconds to dry it out before shutdown.
Use new OEM gaskets only when you put it back together, and make sure the gasket surfaces are clean and flat and you should be fine.

 

[Zackman]

Re: Water in bottom of exhaust manifold

Thanks guys... your assistance is always appreciated.​