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-   -   How do I evaluate exhaust manifold condition? (http://www.mastercraft.com/teamtalk/showthread.php?t=58001)

strad 10-28-2013 09:40 PM

How do I evaluate exhaust manifold condition?
 
This started off as a fix for riser gasket leaks. I removed the first riser and discovered after some inspection that it's basically rotten. The inner casting that separates the exhaust from the water jacket is mostly scale. Looking down inside the manifold from the top into the water jacket, I can see scale and a few rusticles, but it doesn't look as bad as the riser did. There is, however, a LOT of sediment and crap down at the aft end by the drain plug.

I'm going to go out on a limb and guess that the other riser, which I haven't removed from the manifold yet (that's another story lol), looks the same inside. So both of those are getting replaced for sure. Question is, what intelligent ways are there to evaluate the soundness of the manifolds? They are off the engine btw. And there was evidence of exhaust leaks (soot) around some of the ports on each side. So removal had to happen. Believe it or not, only one bolt on each side gave any trouble-- the front one. What I did was remove all the other bolts, then grab the manifold at the aft end and torque it up and down. After that I tried the breaker bar on the bolt again and it broke loose.

This is an 84 PCM 351. While we're on the subject, can any conclusions be drawn from the condition of the riser as to internal condition of the water jackets on the engine -- am I going to have other troubles in other words. I mean the inside of that riser looks a lot like the titanic!

mikeg205 10-28-2013 10:22 PM

3 Attachment(s)
after 10 years you should start inspecting risers and manifolds on an annual basis... mine last year pictured.. doing again this year... they should look like this. If they are completely clogged consider new. if just scaled - consider a bath in evaporust. www.evaaporust.com - non corrosive - I gave block a good sock this season. The orange is permatex.

strad 10-30-2013 06:13 PM

Well after rinsing out the manifolds with water and getting all the loose pieces out, they actually look ok. I ordered the rust remover so I'll hit them with that. The risers are gonzo though. At the aft end where the water exits around the exhaust, the opening was mostly occluded on both sides, although it still flowed water ok. I started working with a screwdriver to get it cleared, and at least one chunk of iron exhaust pipe broke off, and I was being relatively gentle! Clearly rotten. The date stamp on the manifolds is 11/10/83, so we know they are original.

mikeg205 10-30-2013 06:28 PM

Quote:

Originally Posted by strad (Post 988814)
Well after rinsing out the manifolds with water and getting all the loose pieces out, they actually look ok. I ordered the rust remover so I'll hit them with that. The risers are gonzo though. At the aft end where the water exits around the exhaust, the opening was mostly occluded on both sides, although it still flowed water ok. I started working with a screwdriver to get it cleared, and at least one chunk of iron exhaust pipe broke off, and I was being relatively gentle! Clearly rotten. The date stamp on the manifolds is 11/10/83, so we know they are original.

from gonzo to occluded... love it :D:D:D

strad 10-31-2013 03:51 PM

I'm college educated with redneck tendencies ;-). I finally finished cleaning the gasket material off one of them.
29 years of heat made them stick very well! Still have to wire brush a few spots (not on the gasket mating surfaces) before priming and painting the manifolds. It'll be nice to have one more thing sorted. At some point in the past somebody used the straight exhaust hose for the down pipe portion. Both had a kink because they are not designed to bend. But I have the correct hose on the way.

strad 11-03-2013 09:08 PM

Oh crapola. This morning I removed both mufflers from the boat along with the hoses that run to the transom. Got them out, and in the process of separating the first muffler from the hose, lost control of the muffler and the end of it hit the concrete (the downstream end of it). Chipped the flange, took a chunk out of it. As near as I can tell, both hose clamps will actually be able to hit solid material. I do not see any cracks upstream of the chip. I epoxied the chunk back in with marine epoxy. Think I'll be ok running it? Damn those things are brittle. It only fell about six inches!

I did not chip the second one.

Cloaked 11-03-2013 09:12 PM

Quote:

Originally Posted by strad (Post 989388)
Oh crapola. This morning I removed both mufflers from the boat along with the hoses that run to the transom. Got them out, and in the process of separating the first muffler from the hose, lost control of the muffler and the end of it hit the concrete (the downstream end of it). Chipped the flange, took a chunk out of it. As near as I can tell, both hose clamps will actually be able to hit solid material. I do not see any cracks upstream of the chip. I epoxied the chunk back in with marine epoxy. Think I'll be ok running it? Damn those things are brittle. It only fell about six inches!

I did not chip the second one.

It will be fine.

When you reassemble with hoses, use an anti-sieze compound on the hose connections to the riser. Makes them much easier to remove later on.

You can thank me later....

.

mikeg205 11-04-2013 09:03 AM

Quote:

Originally Posted by Cloaked (Post 989390)
It will be fine.

When you reassemble with hoses, use an anti-sieze compound on the hose connections to the riser. Makes them much easier to remove later on.

You can thank me later....

.

NIce idea cloaked - that's why I love this forum. will have to do that next time I inspect... but prolly new hoses in 2015... the a bit of anti seize.

Chipped flange easily repairs with Loctite marine epoxy. You can make a simple mold with some flexible plastic and some wax paper or Saran wrap.

JimN 11-04-2013 09:55 AM

Quote:

Originally Posted by strad (Post 989388)
Oh crapola. This morning I removed both mufflers from the boat along with the hoses that run to the transom. Got them out, and in the process of separating the first muffler from the hose, lost control of the muffler and the end of it hit the concrete (the downstream end of it). Chipped the flange, took a chunk out of it. As near as I can tell, both hose clamps will actually be able to hit solid material. I do not see any cracks upstream of the chip. I epoxied the chunk back in with marine epoxy. Think I'll be ok running it? Damn those things are brittle. It only fell about six inches!

I did not chip the second one.

If the piece was butt-joined, it may not be strong enough but you could back it up with a couple of layers of fiberglass.

strad 11-04-2013 03:33 PM

Yeah what I might do is put a sheet on the inside for reinforcement. I would think the outside would increase the dia too much and I might not get the hose on.


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