350Mag water problems
 

I have a 1986 350 Mag with water under the both valve covers. Replaced the riser and elbow gaskets and flushed the engine. Then we changed the oil. Looks like water is still getting in. Milky oil under valve covers. Oil on the dip stick is ok. Also after we chaged the these gaskets the engine overheats at WOT only. No sign of leaks around the exhaust manifolds. Any ideas ?? :(

Welcome to the OSO board.

Now I am not sure if I am understanding you correctly. I will have to make a few assumptions here. I think you mean that you have water in your exhaust valves, not your heads. By your post, I think that you changed the riser gaskets. I first have to ask you this: When you pulled the risers, did you see water down by the valves? Did you also see water or rust stains leaking down into the manfolds from the riser gaskets? How old are the manifolds and risers? If there is water by the exhaust valves then either the manifold and or the riser is cracked or the gasket was leaking? If when you pulled the riser to change the gasket, you id not see a trail of water or rust seeping down from the gasket, then more than likely the manfolds have rotted or cracked.

Roadrat,

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I was at the boat today and retorked the studs to 25 ftpds. But we are still getting water in. When I tryed to start the engine it locked up so that means I have water in one or more of the cylders. I don't remember seeing and trails of rust when we replaced the riser and elbow gaskets but I really wasen't looking for very hard.. We had a machinc from the marina next store take a quick look at the problem and he thought it was the riser or elbow gaskets. The exhaust manifols are OE so that means they are 16 years old. The engines only have 470 hrs. on them. The boat has alway been in fresh water. Somebody said that I may have to pull my exhust mainfods off to see if there is any damage to them. Again no oil in the crank case.

More than likely the exhaust manifolds are bad and will need to be replaced. Pressure test the engine to make sure that that is not the source of the water. Get the water out of the engine as soon as possible. ( THIS MEANS NOW NOT NEXT WEEK)

Pull the manifolds off right now!!!!! Check to see if the exhaust valves are getting wet. If they are either the manifolds or the risers are leaking. In either case, just by the amount of years you have had them, I would just replace them. If this motor is hydro locking, that means that a good amount of water is getting into the cylinders, there will be water in the oil very soon, if not already.

Thanks guys. Will be pulling the exhaust manifolds off this week. I have noticed that there seem to be some pretty good after market exhaust kits available that may save some $$ over Mercuiser what do you think ?

Spend the money on the aftermarket exhaust.