Water in Exhaust Manifold

[CFD367]

So we bought our 2002 320 Sundancer a few weeks ago and had about a 5 hour ride to bring her home. Boat ran great, we where getting close and I throttled down and shortly after I heard an audible beep and the RPMs on starboard motor dropped like it was going to stall, but I brought it back up and it was fine, this happened probably twice in 15 minutes and then didnt have a problem when I was docking. Next day we went out and had a knocking in the transmission, starboard stalled on me once. Tranny was done this season before I bought it so I was nervous about that. Come to find out the low idle knocking is a fairly common issue thank god. I started to diagnose and couldnt get any change from engine when I pulled the wire from number 8 cylinder. I pulled the plugs, 8 was wet from what appeared and smelt like fuel, 4,6 had some rust on the ends by the last threads the rest looked good. Pulled the riser and there was probaly 2-3 tablespoons of water in manifold for #4,6. risers and manifolds looked to be in decent shape other than the little bit of rust now that water got in there. My question is and any input is appreciated, being a raw water cooled boat is it more likely a cylinder head that rotted out and I am getting water from there? Or would it more likely be the manifolds/3inch riser/elbow and gasket that could be leaking?

 

[scoflaw]

Pressure test the water system. It all can be done at the t-stat housing before you take anything apart. you don't have to put the elbow back on to do this.

 

[CFD367]

Pressure test the water system. It all can be done at the t-stat housing before you take anything apart. you don't have to put the elbow back on to do this.

How do I go about that? water or air? What keeps it from going out the exhaust?

 

[scoflaw]

Air.. Plug the 2 hoses that go to the manifolds and the large 1 from the water pump . Or cap those nipples on the t-stat housing. Pull the 2 npt sensors off the t-stat housing and screw a shrader valve into 1 and a pressure gauge in the other

 

[cfd95]

The transmission is probably fine.
The knocking you're hearing is caused by dead cylinders causing the damper plate to rattle.

 

[370Dancer]

Listen to Scoflaw

 

[johngus]

do compression test.you may have bad valves from the manifold leaking.get on this quick to save the engine.it may just need a valve job with new manifolds and risers