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Manifolds and Risers

J

Jakwi

Member
Hi all,

I noticed that there was a little rust on my starboard side exhaust riser joint.

Temps have been normal, 175-180, probably closer to 180.

I can place my hands on both risers and hold them there. Although the Starboard side is hotter, neither is too hot to touch and I didn't notice any hot spots on the risers or manifolds. From what I've read it is normal for the starboard side to be a bit hotter, although I don't understand why. IE after a half hour running down the river I can still place my hands all over the risers, and manifolds without any issues, temps seem uniform.

That being said, I don't know how long it has been since they have been replaced. I was told that the repower had 30 hours on it when I bought it last summer, but without a meter who knows. I flush the motor every time I use it, by running the engine until it's up to temp on Muffs. The previous owner stressed the importance of this to me so I assume he also did this consistently. The boat is used primarily in brackish water. The motor looks good, runs good, my oil is clean, I pulled the plugs and they looked fine, but I replaced them anyway.

The port side has no rust at the gaskets, I haven't pulled it apart yet, but I will.

I know the safe answer is just to replace them, but on the other hand I don't have the money right now. I can start saving for next year, but if I have to replace them right now, then it will sit this summer, That would be a real bummer.

So my question is, how many years do you guys think are on these manifolds/risers and extensions? I've googled about exhaust riser inspections but all you can find for pictures are extreme cases where they are completely shot, I'd love to see some pictures that show what they look like at the 3 year, 4 year, 5 year inspection points, so that I have a point of comparison.


From my point of view the extensions look fine, The manifolds also look pretty good, although the rust inside shows that my gaskets were leaking.

The risers look rustier, but I couldn't find any rot, looks mostly like surface rust with plenty of meat left. I've posted all of the pictures on imgur. The flapper looks droopy, but I don't know if that is normal.

Thoughts? Thanks for the help.

https://imgur.com/a/6i9E7k5
 
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Jakwi said:
Hi all,

I noticed that there was a little rust on my starboard side exhaust riser joint.

Temps have been normal, 175-180, probably closer to 180.

I can place my hands on both risers and hold them there. Although the Starboard side is hotter, neither is too hot to touch and I didn't notice any hot spots on the risers or manifolds. From what I've read it is normal for the starboard side to be a bit hotter, although I don't understand why.
Un-equal flow!
Typically caused by differences in fittings, hose lengths, a restriction somewhere within the system, etc.
Never restrict the cool side in hopes of lowering the temp on the warmer side.
Find the restriction, and make the correction.

IE after a half hour running down the river I can still place my hands all over the risers, and manifolds without any issues, temps seem uniform.
In looking at your photo, you have exhaust Manifolds, Spacers/Risers and Elbows.
I think that you are referring to your Exhaust Elbows!


That being said, I don't know how long it has been since they have been replaced. I was told that the repower had 30 hours on it when I bought it last summer, but without a meter who knows. I flush the motor every time I use it, by running the engine until it's up to temp on Muffs. The previous owner stressed the importance of this to me so I assume he also did this consistently. The boat is used primarily in brackish water. The motor looks good, runs good, my oil is clean, I pulled the plugs and they looked fine, but I replaced them anyway.
Warm the engine up.
Loosen all exhaust component fasteners.
When things cool back down, remove the entire exhaust system and inspect the manifolds, spacers/risers and elbows!
Each flat mating surface can be dressed up by a machinist using a "surface sanding" machine.
It will take him about 5 minutes per surface.

Now your new gaskets will seal properly.

The port side has no rust at the gaskets, I haven't pulled it apart yet, but I will.

I know the safe answer is just to replace them, but on the other hand I don't have the money right now. I can start saving for next year, but if I have to replace them right now, then it will sit this summer, That would be a real bummer.

So my question is, how many years do you guys think are on these manifolds/risers and extensions? I've googled about exhaust riser inspections but all you can find for pictures are extreme cases where they are completely shot, I'd love to see some pictures that show what they look like at the 3 year, 4 year, 5 year inspection points, so that I have a point of comparison.
Due to the variations in cast iron (nickel content), every one's answer will be different.


From my point of view the extensions look fine,
What you are calling extensions are also your Spacers/Risers.

The manifolds also look pretty good, although the rust inside shows that my gaskets were leaking.
Yes.... after you have the mating surfaces dressed up, this area should no longer leak.

The risers look rustier, but I couldn't find any rot, looks mostly like surface rust with plenty of meat left. I've posted all of the pictures on imgur. The flapper looks droopy, but I don't know if that is normal.

Thoughts? Thanks for the help.

https://imgur.com/a/6i9E7k5
Click to expand...
 
Hi Rick, looks like my terminology is a little mixed up.

I can place my hands on any part of the exhaust system after running down the river. The starboard side is hotter then the port side, but each side is uniform in temperature no matter where I put my hands on that side. I was feeling for hot spots, but the entire manifold feels the same temp all over the spacer/riser feels the same on all sides and the elbows. So at least from a flow stand point it seems good. While there is some rust in the water passages, I don't see any obstructions that would limit flow. Although I guess it's possible its down in the manifold, but it seems like there would have been a hot spot if there was a blockage.

As far as removing the manifolds, I'm not sure how I could warm up the engine with it all apart like this. Is it out of the question to remove the manifold bolts with the engine cold?

Thanks for the help.
 
Last edited:
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Jakwi said:
Hi Rick, looks like my terminology is a little mixed up.
You are not alone. But that's OK..... many do the same!



As far as removing the manifolds, I'm not sure how I could warm up the engine with it all apart like this. Is it out of the question to remove the manifold bolts with the engine cold?
No... it's not out of the question.... just be careful.
You may have rust/corrosion at the threads that you will be fighting against.
Whereas if you heat things up, your chances of removing bolts without issue are much better.

Thanks for the help.
Click to expand...
 
Thanks Rick,

So at least at this point, I'm not getting the Oh my god you can't put those back on response. Is that an endorsement that they at least look ok?

And what do you mean by be careful. Slow steady pressure? is there a particular order?

Or is there a way for me to run the engine with the one side manifold disassembled? I wish I had realized, it would have been very easy to warm up to begin with. :/
 
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