Exhaust Manifolds and risers on 4.3L, how to tell when they need to be replaced?

denhajm

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Okay, got a good file, started working on one of the risers. What do you think from what you see here?
 

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denhajm

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Are my risers and manifolds done here? Too thin of wall between passage? I use this boat ~ 10-15 hours a year is all. Thinking of 2-3 more years then getting something newer. But willing to install new parts if truly necessary. I notice a big price delta between Mercruiser exhaust manifolds & risers compared to aftermarket. Thanks for the help.
 

alldodge

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I think some of the guys which previously commented are not in today, or something else is taking their time. My impression is replace them but I'm not the expert, just the walls look thin to me. One of the elbows look pretty clogged
 

Bondo

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Ayuh,.... The inner gasket surface looks to be well over 1/2 gone,.....

They might run abit longer, but I wouldn't take that chance,.....
 

denhajm

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Okay, I hear what Bondo and AllDodge are saying--and I thank you for your input. So, are Mercruiser OEM exhaust manifolds and risers worth the extra $500 over 3rd party (GLM, Sierra) exhaust manifolds and risers?
 

alldodge

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They can all work, some aftermarket have issues with flatness. So if you get the aftermarket makes sure to take a file to the tops as you did with the originals. This way if there is an issue you will have found it prior to installation.
 

Bondo

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Ayuh,.... I bought GLMs along time ago, 'n found the inner gasket surface was 'bout .020" lower than the outside,....

A trip to my local machine shop, 'n a few minutes on their monster belt sander fixed 'em,....

Been Ok since,...
 

bruceb58

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Last edited:

denhajm

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Nov 24, 2012
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denhajm

Seaman
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Nov 24, 2012
Messages
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Okay, ordered Mercruiser manifolds and risers yesterday and they arrived on my door this morning! How's that for service--less than 24 hours! Here are some photos comparing new risers vs. what I had. Do these old risers and manifolds have any residual value? I expected a bigger difference in gasket seating surface area between the old and the new. Anyway, they're here now so I'll pull the old exhaust manifolds off too and install the new parts (but not before I check my shutters).
 

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