2000 38 DA 7.4 Horizon Water Ingestion

H

Hardliquor

Member
Jul 6, 2009
34
Elk Rapids, MI
Boat Info
380 Sundancer 2000
Engines
454
I have a 2000 38 DA with twin 7.4 horizons with closed cooling. I am getting water in the exhaust. I have taken the complete manifold, riser and elbow from the starboard engine and placed it on the port engine. after running the engine for 5 minutes ate the dock, the water fills into #5, then over to #7 in the bottom of the runners. I started the engine cold and felt the bottom of the exhaust manifold, the part with no water jacket around it and can almost instantly tell that #5 is cooler than the others as the engine comes up to temperature. This shows that the water is cooling down the manifold. Has anyone else had this problem? I have seen the other thread on water ingestion on the 310 models and looks to be muffler related. Any help would be appreciated.
 
You have either a bad gasket between the riser and manifold, a bad gasket between the riser and elbow, or a bad manifold, riser, or elbow, or a combination of these are bad.

The cure is frequent replacement of the exhaust system. Elbows should be used for no more than five years. Manifolds can go longer.

The exhaust system problem to which you allude is a problem where either water runs forward in nearly horizontal exhaust pipes when the boat is slowed suddenly or when a mist of water is ingested into the engine because of longer valve overlap with the GM Generation VI and L-29 engines. This is most likely not your problem. You probably have corroded exhaust components.

If you do have water leaking at that rate, then you have a significant problem that if unresolved will result in not only having to replace the exhaust system (a couple grand) but also a head job (another couple of grand) and if the engine gets significant water into the cylinder bore that results in either rusted cylinder bore, rusted rings, or hydrolocking, a complete engine rebuild. (Several grand)
 
I removed the complete exhaust (manifold, riser and elbow) complete, without breaking them apart from the starboard engine which had no water in it. I installed it on the port engine, (my problem engine) and got the same results; water in the exhaust after only a few minutes on running at the dock. The complete manifold set up works fine on the starboard side. I'm really confused and none of the techs I've talked to have ever heard of it.
 
Are your exhausts raw water or are they fresh water cooled, mine were converted to all fresh water. Can you tell if this is sea water or antifreeze in the manifold?? How do you know the manifold you took from the other side was not leaking? Maybe it just wasn't symptomatic? How old are the components (i.e. elbows, risers, and manifold)? Give a little more background.
 
The manifolds are lake water cooled. The water is sucked up from the sea water pump, goes through the trans cooloer, through the fuel cooler, into the coolant heat exchanger, into the bottom of the manifold, out the elbow, into the muffler and back into the lake. The components are original, however we are in fresh water and only get about three months of boating annually. I know the other manifold is good, because it works fine on the other engine. The water that is coming in is definitely lake water.
 
Did you do a compression check yet? Wonder if an engine problem is pulling exhaust (and cooling water) back towards the engine.

You might be able to see something with a borescope, but I think the exhaust gas temperatures would damage the scope. Never tried it. I've inspected the exhaust right after shutting down with the scope, but not with the engine running.
 
Could there be an exhaust restriction on that side? Do you have visible water exiting on that motor? How does the flow compare with the other engine?

It seems swapping the manifold/riser combo has eliminated them from the equation.

Doug
 
Yes on the compression test, all good except for #5 & 7, they were at 100, not 125. I do think the engine is pulling the water back in, that's the only place it can come from. Can a head gasket cause this? I am getting a bore scope to check it out further.
 
I don't think water would stay at the bottem of the maifold if the engine was runing and that cylinder was firing. How are you diagnosing that the water is really there? I would do what Frank said and get a borescope in there and see what is going on in there. If your elbows are original I am not sure they have the inspection hole on the top.
 
Oil is fine, not milky. I can pull the manifold off after running it and see the water laying in it. I am leaning toward a split in the gasket between #5 & #7.
 
I would think if your talking about a split in the head gasket between 5 & 7 that they would have the same compresion numbers. Do you have the lift type mufflers or the log? These motors are known for ther valve overlap and will cause a suction at shut down.
 
Hardliquor said:
Oil is fine, not milky. I can pull the manifold off after running it and see the water laying in it. I am leaning toward a split in the gasket between #5 & #7.
Click to expand...

That would make sense only you said you swapped the manifolds from one working engine to the non-working engine. Unless both manifolds suffered from the same condition....??

Doug
 
What size riser blocks do you have? Up till now did you get the correct WOT RPM on this motor (4400-4800)? What gave you the indication that there was a problem originally?
 
I have fixed the water ingestion problem; quite a while ago but have not had the chance to share the fix with everyone (boating seasons are short enough in northern mi.)
the problem was a spark plug wire that went bad and caused #6 cylinder to quit firing, that said #6 acted as an air compressor and pulled water back up through the exhaust and would lay in the bottom of the exhaust runner, until full then work its way into the next easiest runner. I had a freind print off all probble causes of water ingestion and that was one of the causes. I found only one "old timer" mechanic that said it could happen; everyone else (including mercury) said this could not happen. I OHM tested the wire and could not believe it; alls well thatends well. sorry it took mesolong to post the fix but I hope it helps someone in the future.
 
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