Water in manifolds

[Moose]

I have just purchased a 2003 Maxum 2900 SE I haven't taken possession yet as owner still making repairs. It has twin mercruiser 190 hp 4.3 litres v6 tks engines raw water cooled. Bothe legs are bravo 2 and they have both just been fully rebuilt and the engine shafts replaced. While working on back of engine the mechanic removed the riser to gain access to rear of engine he found water in the manifold and after an engine compression test found 1 cyclinder a little down in compression with evidence of water in cyclinder the manifolds and risers were checked and are ok. There is no water in the engine oil? What do you think went wrong we are thinking a head gasket oh engine done 420 hours.

[gmc60]

Your manifolds or risers are leaking replace them i say ???

[mmwjr]

A leaking gasket between the manifold and riser if wet exhaust can cause this.

Cylinder one is down so either the head gasket is going or most likely the exhaust valve is bad from burning water due to the bad exhaust gasket.

Has the exhaust ever been changed? It's due if origional and that's both engines.

I say the head needs to come off and rebuilt and the entire exhaust should be replaced.

Very common to see a tuliped exhaust valve at 500 hours due go leaking exhaust in a salt water boat.

[Moose]

The manifold and riser have been assessed and all ok. Only 1 cylinder has been effected. Water was noticed in the manifold but manifold ok. Water detected I only 1 cylinder exhaust system would not have been looked at

[Moose]

Head Bing assessed this Tuesday so will no more I guess by then

[mmwjr]

Don't care what the mechanic said if salt water cooled the exhaust is nearing end of life with that many hours and still origional.

Your money do as you please just giving you my advice. But as yourself where did the water come from? This is the normal telltale signs of an exhaust leak and yes common that one cylinder only gets water in the beginning stages.

[Moose]

Just thought I would update appears the mechanic used to much pressure when flushing test engine. Water was for through the open exhaust valve. Head has been removed cleaned and valves re seated. Work almost completed both engines out the boat and full check up out the engine bay being done. I hope to have boat going in a week. Thanks for input

[speedysprocket]

Is there a way to quantify the life remaining of a manifold? Where do they leak from when they rust too much?


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[mmwjr]

Originally Posted by Moose

Just thought I would update appears the mechanic used to much pressure when flushing test engine. Water was for through the open exhaust valve. Head has been removed cleaned and valves re seated. Work almost completed both engines out the boat and full check up out the engine bay being done. I hope to have boat going in a week. Thanks for input

Not sure I understand. The elbow injects water into the exhaust stream on the downward bend so even high pressure flow should just shoot into the y-pipe and out the drive. What is the explaination on how water got back into the engine?

[mmwjr]

Originally Posted by speedysprocket

Is there a way to quantify the life remaining of a manifold? Where do they leak from when they rust too much?


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No easy answer but elbows go first. Another common area is the wet joint interface as the wall thickness lessens the gasket cannot provide a hood seal.

BB one I have seen crack around the raw water input.

[speedysprocket]

Originally Posted by mmwjr

No easy answer but elbows go first. Another common area is the wet joint interface as the wall thickness lessens the gasket cannot provide a hood seal.



BB one I have seen crack around the raw water input.

Well my elbows are stainless, so they're perfect. One set of manifolds is getting thin between the exhaust and water jacket at the gasket surface, though. Was wondering if there's any guideline on what is too thin.

[mmwjr]

Originally Posted by speedysprocket

Well my elbows are stainless, so they're perfect. One set of manifolds is getting thin between the exhaust and water jacket at the gasket surface, though. Was wondering if there's any guideline on what is too thin.

Not that I am aware of but ask yourself this; how much do you want to gamble on a damaged engine.

[Cool Beans]

The exhaust on my 2001 SCR2500 took 13 years to go. Although they did not leak, flakes of rust clogged the water passage holes allowing the rubber goods downstream of the risers and elbows to melt and fail. Water pump although in poor condition lasted 13 years due to unscrupulous mechanic! Yea, we changed the impeller... Not.

[shrew]

Raw water cooled manifolds and risers in saltwater are typically replaced every 5-8 years. I've replaced a set at 11 years which needed them badly and a set at 8 years, which also showed signs of needing replacement.

[Cool Beans]

Just a quick disclaimer- if you're not doing the maintenance yourself, ensure your mechanic is. While I don't recommend going to end of life on your cooling system (you could be a large towing bill away from your marina (mine was an $800 tow) the consensus seems to be 2-3 years on the impeller and as Shrew indicated, 5-8 years for Manifolds, elbows, risers... etc. Some pictures are in the Cool Beans Gallery
Happy Boating!