1999 454 Mag MPI just quits - videos

Heads off, and waiting for OE new replacements. A bit distraught. No breaks in any gasket or anything obvious for why exhaust water got into #5, except through reversion, or perhaps a bad exhaust manifold/riser/extension/gaskets. They are new, with about 2 hours on them. The valve was rusted halfway open, so it didn't hit the piston. I'm inclined to add a 12" extension of the exhaust at the elbow to move the mix downstream towards the waterlift. 2" od SS tubing is too small. Anyone have a spec on the id of the exhaust on the elbow? 3" perhaps?
#5 corrosion - reversion.PNG
valve suck half open.PNG
 
Why is #7's exhaust valve open? Definitely looks like #3 and #5 were getting water in them. As to where it came from.....I would definitely go through the exhaust hoses and make sure the liner has not collapsed backing up the water to the riser.
 
Why is #7's exhaust valve open? Definitely looks like #3 and #5 were getting water in them. As to where it came from.....I would definitely go through the exhaust hoses and make sure the liner has not collapsed backing up the water to the riser.
We were banging on them. Not good. That’s why I’m pressure testing the manifolds risers and extensions. and just replacing both heads. Do over.
 
Why is #7's exhaust valve open? Definitely looks like #3 and #5 were getting water in them. As to where it came from.....I would definitely go through the exhaust hoses and make sure the liner has not collapsed backing up the water to the riser.
This is good advice. On my boat, the small exhaust that connects to the side outlet had the inner lining come away from the outer lining. Instead of a circle, my exhaust was only able to go through a thin crescent moon. It was not until I removed the whole exhaust line and looked through it that I saw this collapse. Looked and felt fine on the outside.
 
hmmm.....
That hose is new, probably around Feb or March of this year.
Water was up in the intake plenum (see pics above of the intake side of the heads)
this was pretty sudden. The only running that engine has done, was getting me over to the crane to put the new Port one in, and back. About a mile.
as usual, everything is suspect now that has anything to do with raw water.
 
This is good advice. On my boat, the small exhaust that connects to the side outlet had the inner lining come away from the outer lining. Instead of a circle, my exhaust was only able to go through a thin crescent moon. It was not until I removed the whole exhaust line and looked through it that I saw this collapse. Looked and felt fine on the outside.

Did you shoot a picture of it? I keep meaning to do it when I see it just to show people what to look for.
 
How would water end up that high in the engine? I assumed it was just condensation from a cold engine block. If it was that high, the entire pan would be full of water. Or am I missing something?
 
How would water end up that high in the engine? I assumed it was just condensation from a cold engine block. If it was that high, the entire pan would be full of water. Or am I missing something?
Mysteries to be solved.
It has only run for seconds since the pushrod got bent during a start. Pushrod bent because valve rusted to head, and didn't move when everything else did. It is stuck slightly open. Engine ran without fault prior to this. Only thing in between good running and bent valve, was I changed the manifolds, extensions, and elbows prior to trip over to the crane.
Either reversion, or a failure in the manifold water jacket. No sign of any gasket leaking as I tore down that side. No failures in the head gasket or intake gaskets that we can see.
That is why I keep circling back to the manifold. I will pull the hoses off the water lift muffler and see if something is amiss, but as I said, that hose is new, and is good hose.
 
Did you shoot a picture of it? I keep meaning to do it when I see it just to show people what to look for.
I found one of a boat I worked on. Someone let an engine overheat. Both tubes after the risers were like this.
 

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Mysteries to be solved.
It has only run for seconds since the pushrod got bent during a start. Pushrod bent because valve rusted to head, and didn't move when everything else did. It is stuck slightly open. Engine ran without fault prior to this. Only thing in between good running and bent valve, was I changed the manifolds, extensions, and elbows prior to trip over to the crane.
Either reversion, or a failure in the manifold water jacket. No sign of any gasket leaking as I tore down that side. No failures in the head gasket or intake gaskets that we can see.
That is why I keep circling back to the manifold. I will pull the hoses off the water lift muffler and see if something is amiss, but as I said, that hose is new, and is good hose.

I don't think the water is coming from the intake manifold. If you turn the head around I will bet the intake runners do not have rust on them.

Something backed the water up. Your engines I do not believe have a known reversion issue so how did the water get there? Additionally from what you have said the rust is only on one head and the exhaust manifolds and risers are new.

I would flood the exhaust hose on the offending head with water. If that checks out it has to be the riser, exhaust manifold or manifold/riser gasket that is leaking water.

My money is on the manifold/riser gasket leaking. I have seen brand new exhaust manifold and risers leak with manufacturing defects but I don't think that is the problem you have. A look (picture) down the riser port on the exhaust manifold of the offending head would probably confirm the issue.
 
Boy that is something I've never seen before.


I have seen it four times. The last time was a month ago on my generator exhaust hose. The outside of the hose was leaking water and looked fine otherwise. The interior liner had collapsed and water was leaking out between the liner and the outside of the hose.

Exhaust water flow was off and inconsistent. On a main engine ......that condition can result in disaster pretty quickly if the boat is at speed.

The exhaust hoses take a lot of abuse especially the ones that connect to the risers.
 
I don't think the water is coming from the intake manifold. If you turn the head around I will bet the intake runners do not have rust on them.

Something backed the water up. Your engines I do not believe have a known reversion issue so how did the water get there? Additionally from what you have said the rust is only on one head and the exhaust manifolds and risers are new.

I would flood the exhaust hose on the offending head with water. If that checks out it has to be the riser, exhaust manifold or manifold/riser gasket that is leaking water.

My money is on the manifold/riser gasket leaking. I have seen brand new exhaust manifold and risers leak with manufacturing defects but I don't think that is the problem you have. A look (picture) down the riser port on the exhaust manifold of the offending head would probably confirm the issue.
Definitely not FROM the intake. Raw water wound up in the intake plenum. The Gen VI 454 is THE poster child of reversion, from go fast boats to the 370. (Read through Offshore Only. Tons of examples) The exhaust hose is about 3 feet long, straight, and very easy to see. There was no standing water at the top of the inlet to the water lift muffler, and the amount of water was not catastrophic, as the engine was not running very long, nor was it at speed. All checks of the lower end look good. No water in the oil.
My working theory (for now) is that reversion (or something) sent water into the exhaust valves on that side. At some point after the valve got stuck half open on #5, running the engine, even for less than a minute, let water back into the intake plenum, and the other intakes were creating enough vacuum to distribute the water around the other intake ports and leave residual in the plenum. If not reversion, then it would have to be somewhere in the exhaust manifold exit system. That's why I am still looking into these brand new manifolds, 6" extensions, and elbows. That's also why I am more than curious about extending the mixing point of water and exhaust down stream towards the water lift mufflers with a SS tube hammered and welded into the elbow. If you have followed me for the 20 years I have owned this boat, I got it with engine set number 3 in it, as a result of serious reversion due to the log exhaust setup. Urban legend is that my boat was the first one that Sea Ray and Mercury finally admitted to the exhaust setup, and switched to water lift mufflers and 6" extensions. Can't prove that on paper. These engines, under my watch lasted about 17 years before the port destroyed a valve due to reversion. I found a 1999 matching set from a LA fire boat, and they ran good for a while, but alas, the seller was not forthcoming about the true condition of those engines, which led to this thread, and the ultimate replacement of the port engine (spun main crank bearing).

So, all things point to a failure in the raw water circuit, that has locked up the valves enough for me to shell out another few boat bucks, and start over with the top end of the Starboard engine. Covid, and surprise health issues have stretched this saga out way longer than I had anticipated. That said, I have been getting great fuel economy for the past 3 years. When I'm done or dead, this vessel will be better than new from bow to stern. Isn't that what hobbies are for?

water in intake plenum1.jpeg
 
My point is that you have had multiple engines and 20 years of ownership without a reversion problem showing up. So why did it happen after you changed the exhaust manifolds and risers? That is the part I am struggling with.
 
This is a closed cooling system, correct? So a leaky intake manifold seal would not cause this because I don't see anything green, and we didn't see anything in the lifter valley?

If we didn't see anything in the lifter valley, it HAS to be something with the exhaust.
 
My point is that you have had multiple engines and 20 years of ownership without a reversion problem showing up. So why did it happen after you changed the exhaust manifolds and risers? That is the part I am struggling with.
So am I. Not 20 years though. Set 1 and 2 were reversion within the first 5 years with the PO. Set 3 went from 2003 to 2017 then reversion in the port engine, and set 4 had a different issue in the port (spun bearing), and now the set 4 Stbd just went tits up with the reversion you see. Points even harder to a bad part in the exhaust circuit. Testing will see. So, let's change the subject. What tool(s) do you use to block openings and inject air/water/acetone into a suspect manifold? Extension? Elbow? Procedure? I can guess and make shit up, but if you have a method, let's hear it.
 
View attachment 152349
Looking at not only the port circled, but all of the port's and mating surfaces.
How long has this head been in service?
Can’t give you 100% answer.
1999 engine, looks original. 2017 til now under my watch. Not run much from 2020 til this year, and that was an hour or so at idle to 2000 rpm
 

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