Exhaust Manifolds causing water ingestion?

[Gunn]

Hey all, back in late 2018 one of the 4.3MPI engines on my boat suffered hydro-lock. After removing the spark plugs, there was water in the #2 and #4 cylinders. I got it running again and it ran just fine. A couple of weeks later it happened again. And then again. When I finally brought the boat home on the trailer, it was dead (the low oil pressure alarm sounded and it started stalling). Long story short, I purchased a remanufactured long block. In disgust, I let the boat sit for all of 2020 and so far, 2021.

I have removed the engine and just today finished the tear down and removed the starboard side cylinder heads. All 3 cylinders were massively corroded due to the brackish water ingestion. But no smoking gun. I fully expected to find a pathway from the water jacket into the cylinder head, or from the water jacket in the block to the cylinder bore. But it all looks well sealed, no pathways above or under the head gasket.

So now I'm wondering...could it be my brand-new HGE EDP-coated dry-joint exhaust manifold, spacer and riser? I say brand-new because they were replaced about 2-3 months before the water ingestion occurred. Coincidence?! Maybe. Or maybe they were the root cause. They only have about 5 hours of use on them. I replaced them as a preventative maintenance items, go figure.

I unbolted the pieces to check the condition of the gaskets and see if there was any smoking gun there. But all of the gaskets looked great. Could there be something else with this manifold that I just can't see? Or should I not worry about them, reassemble with new gaskets, and quit worrying about it? (I also wonder if I placed the restrictor gasket in the right place, in the right orientation, if it matters, and if that could have caused water injestion...).

To be honest, I'm unfamiliar with what even the "dry-joint" means, and how the water flows throughout these things, and where failure might occur to cause water ingestion...

Any help you all can provide would be greatly appreciated while I re-assemble my boat!

Tom

 

[scoflaw]

You should have pressure tested the water side of the engine before you took it apart. I would def do that after reassembly before running it.

 

[saopm]

Is that a crack in the spacer to riser joint pic? Inside, top left? Hard to tell from just a pic.

 

[Gunn]

You should have pressure tested the water side of the engine before you took it apart. I would def do that after reassembly before running it.

That's a great idea. It seems that pressure testing of either the manifold, or the whole thing is in order.

I've found videos of people pressure testing just the exhaust manifold. I wonder if I can pressure test all 3 of my components, fit together? I'm going to mess with it and see...

 

[scoflaw]

Absolutely, use the 2 npt ports on the t-stat housing and plug the 2 hoses going to the ex. manifolds

 

[Bt Doctur]

I see no evidence of water in the manifold. So suspect a cracked head or head gasket if it ever overheated or a very low transom and heavy wave action

 

[Bt Doctur]

hThe term Dry Joint Exhaust refers to MerCruiser’s patented exhaust system which utilizes 2 coolant passages vs 4, between the manifold and riser that are separated outside of the exhaust gasket. The benefit is that this eliminates the possibility of coolant leaking into the exhaust passages through common gasket failures.
ttps://www.perfprotech.com/blog/boat-and-engine-technical-tips/marine-exhaust-systems/mercruiser-exhaust-systems-position-of-the-restrictor-gasket-versus-full-flow

 

[dan313]

I had that happen to me. I had 3in spacers and had to add 4.5in spacer to prevent that from happening again. My risers are now 7.5 in high. On certain boats the motor sits too low in the water and you have this issue. Hope this helps.

 

[Wanderer 290]

I had that happen to me. I had 3in spacers and had to add 4.5in spacer to prevent that from happening again. My risers are now 7.5 in high. On certain boats the motor sits too low in the water and you have this issue. Hope this helps.

Plus 1 on taller spacers. My 01 290 DA came with 3” spacers and I was experiencing reversion. With some modifications I was able to install 6” spacers and the reversion has been eliminated. The exhaust manifolds have a plug for egr installation and I occasionally remove those for a quick visual check to verify that no water is accumulating in them.

 

[Gunn]

Plus 1 on taller spacers. My 01 290 DA came with 3” spacers and I was experiencing reversion. With some modifications I was able to install 6” spacers and the reversion has been eliminated. The exhaust manifolds have a plug for egr installation and I occasionally remove those for a quick visual check to verify that no water is accumulating in them.

Wow, just looked up "reversion". So am I to understand this correctly in that the water that seems to exit into the main exhaust stream at the end of the elbow, is somehow being sucked back into the elbow -> riser -> exhaust manifold -> cylinder head ? Would would cause this on a stock 4.3MPI in a boat that ran fine for 15+ years?

I'm getting ready to put the new/remanufactured engine back into the boat. For piece of mind, I ended up purchasing (just last night) new Mercruiser OEM brand riser, 3" spacers and exhaust manifolds for this engine. It was a really difficult decision, as I spent ~$1,300 on the HGE brand components in 2018 and they literally have probably 3-5 hours on them. I shopped around and was able to get everything for $1,888.00 . That pretty much drained by play money account. But at least when I put this new engine in, I'll know it is all-new.

Thanks for the responses!

 

[Wanderer 290]

Wow, just looked up "reversion". So am I to understand this correctly in that the water that seems to exit into the main exhaust stream at the end of the elbow, is somehow being sucked back into the elbow -> riser -> exhaust manifold -> cylinder head ? Would would cause this on a stock 4.3MPI in a boat that ran fine for 15+ years?

I'm getting ready to put the new/remanufactured engine back into the boat. For piece of mind, I ended up purchasing (just last night) new Mercruiser OEM brand riser, 3" spacers and exhaust manifolds for this engine. It was a really difficult decision, as I spent ~$1,300 on the HGE brand components in 2018 and they literally have probably 3-5 hours on them. I shopped around and was able to get everything for $1,888.00 . That pretty much drained by play money account. But at least when I put this new engine in, I'll know it is all-new.

Thanks for the responses!

The link demonstrates reversion.

https://www.cpperformance.com/t-what_is_exhaust_reversion.aspx