8.1 motor checking risers....should i do all 4?

D

DaltonGang

Member
Aug 11, 2020
104
Boat Info
1995 SeaRay 370 Sundancer
Engines
8.1 Horizons
I have 8.1L engines from 2015 with 150 hours.
I think its time to check risers but I don't have the 6 inch risers on mine. Just the manifold to the exhaust elbow. See the link below, it looks like that.

So in order to do all 4 I know I need 8 new gaskets but there's the metal ones called turbulators (or something like that) which goes between the gasket. Do you think i need to replace those also? Thought I read those get ruined when removing stuff.

Lastly, if I pull the elbow off and all look ok then no reason to pull manifolds right? I'm assuming I'm looking for pitting, rust, corrosion. Should I do all 4 or just 1 each engine?


https://www.mercruiserparts.com/bam/subassembly/31676/11838/160
 
You should be able to clean up the turbulators and reuse them. Mine have been through many inspections and two sets of manifolds. For inspection, there's no reason to remove the manifolds. Pulling the manifolds will not give you a better look into the water chamber. A borescope would be helpful. Use caution when cleaning the mating surfaces between the elbow and manifold. Those surfaces need to remain smooth and flat. I pulled all four for inspection. The corrosion always seem similar to me. But, I've read that each elbow-manifold pair should be inspected and not to assume they all ware the same. For the cost of gaskets it would be best to inspect all four. Good luck!
 
kap2 said:
You should be able to clean up the turbulators and reuse them. Mine have been through many inspections and two sets of manifolds. For inspection, there's no reason to remove the manifolds. Pulling the manifolds will not give you a better look into the water chamber. A borescope would be helpful. Use caution when cleaning the mating surfaces between the elbow and manifold. Those surfaces need to remain smooth and flat. I pulled all four for inspection. The corrosion always seem similar to me. But, I've read that each elbow-manifold pair should be inspected and not to assume they all ware the same. For the cost of gaskets it would be best to inspect all four. Good luck!
Click to expand...

ok, if I reuse the tubulators then I'd do all 4 for sure. That's just mostly labor. I thought they'd be ruined during the process because of the gaskets. Maybe I'll get lucky and they will be easy to clean.

To be honest, I'm not even sure what I'm looking for. You said a borescope would help and I actually have one but what I am looking at? Put it down the water chamber of the manifold?
 
Hold on. I just reviewed your the link you supplied that represents your manifolds and elbows. You have what is referred to as "dry joint" system. Sea water does not pass through the joint between the manifold and elbow. You will only be able to look at the exhaust port for cracks or corrosion caused by exhaust gas.

You could use your scope to look into the hose connections to look for excessive corrosion, the cast iron flaking off, etc...
 
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kap2 said:
Hold on. I just reviewed your the link you supplied that represents your manifolds and elbows. You have what is referred to as "dry joint" system. Sea water does not pass through the joint between the manifold and elbow. You will only be able to look at the exhaust port for cracks or corrosion caused by exhaust gas.

You could use your scope to look into the hose connections to look for excessive corrosion, the cast iron flaking off, etc...
Click to expand...

When you looked at that diagram, just note, I don't have that riser piece that is split away from the rest of the diagram. In other words, my manifold goes straight to elbow. So that's a dry joint system?
 
kap2 said:
Hold on. I just reviewed your the link you supplied that represents your manifolds and elbows. You have what is referred to as "dry joint" system. Sea water does not pass through the joint between the manifold and elbow. You will only be able to look at the exhaust port for cracks or corrosion caused by exhaust gas.

You could use your scope to look into the hose connections to look for excessive corrosion, the cast iron flaking off, etc...
Click to expand...

So you are saying I don't really even need to remove the elbow to inspect? I can just undo the hoses and peek in and look for issue. I didn't realize these were dry joints but looking it all over, yeah, you are right. For once, thats a nice surprise. The engines are dated 2015 so I guess by then they learned how to do it better.

So now I'm just wondering if I should even pull the elbow. I'm only asking this because I thought my mechanic surveyor told me to check the risers/manifolds.
 
If your manifolds are raw water cooled you need to check them out real good. The stainless elbows can crack. Peeking in hoses isn't going to work
 
scoflaw said:
If your manifolds are raw water cooled you need to check them out real good. The stainless elbows can crack. Peeking in hoses isn't going to work
Click to expand...

If I've read correctly the dry joint system drains the water back out to the dripless when the engine is off which should really help. They are both 5 years old and 150 hours. Compression is perfect, no overheating, oil samples came back perfect in one engine. In the other it had some sodium. I may check the manifolds in that engine if anything. Maybe I'll bring the mechanic down once I have the elbow off and let him poke around.
 
Peeking and poking ain't the way to go. Salt water manifolds have a life expectancy of around 5 years depending where you live. Things are perfect now, but.... Dry-joint is a step ahead of its predecessor where the exhaust and water were separated by a gasket and the 2 sealing surfaces, but manifolds rust from within and you can't see that. That's why you just replace them at a certain time intervil
 
Agree with scoflaw... I replace mine every 5 years. Once they fail, its too late. Salt water will enter the engine via the exhaust vales and after that it gets ugly fast.
 
kap2 said:
Agree with scoflaw... I replace mine every 5 years. Once they fail, its too late. Salt water will enter the engine via the exhaust vales and after that it gets ugly fast.
Click to expand...


So you guys replace both the manifolds and elbows?
 
My elbows are cast like the manifolds so yes I replace everything. I believe your elbows are stainless and I'm not sure of their life cycle.
 
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I’ve got original stainless elbows from 2005 on my boat as you should too. I inspected them when I replaced all 4 manifolds back in 2017, and they looked practically brand new. I also have the dry joint manifolds and swap them every 5 years.
 
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M Prod said:
I’ve got original stainless elbows from 2005 on my boat as you should to. I inspected them when I replaced all 4 manifolds back in 2017, and they looked practically brand new. I also have the dry joint manifolds and swap them every 5 years.
Click to expand...

My boat is a 1995 370 but sometime after 2015 the owner repowered the boat with 8.1L engines then barely used it. So I don't know if the elbows are original but I highly doubt it. The black on them shine like no other part of the boat.

ok, well sounds like I need to consider replacing all of the manifolds just for safe measures.
I'd hate to be the new owner of this boat and ruin an engine the first year. My wife would kill me!
 
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