Exhaust Manifolds.. to replace or not!

[lostmyedge]

I spent the day pulling the risers off of my Mercruiser 5.7L V8. The risers look pretty trashed, water jackets farily clogged but on the bright side completely intact and no water penetration into the exhaust manifold.

I wire wheeled the manifold as best I could and cleaned the water jackets in the exhaust manifold as best I could (see pictures attached) but they are not perfect and I am wondering if they are going to be good enough to make a water tight connection between the risers and manifold to ensure there is no water leakage into the exhaust chambers.

A few questions:
1. Do they look good enough to mount risers and new gaskets on?
2. Is there a gasket sealer I should use to help ensure they are water tight when I put the new gaskets on?
3. If they should be replaced, can you get remanufactured or do you have to (gulp) buy them new?

Any ideas, advice, help would be much appreciato!!

Thanks

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[img]file:///C:/stbd.jpg[/img]

[JAGSARE1]

Personally, I do not believe you can look at them and determine if they are still good. Think about it this way, they could "look" great today and that unseen thin metal could give way the next time you run the boat.

How old are they? If in salt water and over 5 years old, no question, replace them. I know, probably not what you wanted to hear. Good luck.

[jobowker]

Replace them! If you think manifolds are expensive, you definitely don't want to skip it and then pay for a set of gaskets, and then another set of gaskets & manifolds when they started leaking down the exhaust port, new plugs, new intake manifold gasket ($100 for that puppy), and a tulipped valve & a head job.

[mole2]

If the risers were clogged with rust then they are trash. Same with the manifolds. If I were you I would replace the manifolds and risers. It's a small amount compared to the price to fix the damage should they fail. If they're five years or older they are due anyway.

By the way, you're pictures aren't showing. You must host them somewhere on the inet to display them here...not on your computer.

[chuck34]

There's one very important piece of info you left out....RWC or FWC?

[prockvoan]

Go ahead in spend the $500 now or pay $3000 sooner or later.Osco makes good sets!

[FearNaut]

I'm with everyone else - replace them now, even if they look fine. The alternative is WAY more expensive

[lostmyedge]

Thanks for the advice, It looks like I will be replacing them. I knew in the back of my mind I would have to but I just could not get past the $$$ ringing in my head.

[68stang]

Two years on risers, four on manifolds, as a rule of thumb.

[prockvoan]

68stang - 8/14/2006 10:47 AM

Two years on risers, four on manifolds, as a rule of thumb.

If they are raw water cool.

[68stang]

prockvoan - 8/14/2006 10:58 AM

If they are raw water cool.

[JAGSARE1]

All risers and manifolds are RWC even if the engine is FWC. The block is FWC.

[3bees]

It can be just block fwc or block and manifold depending on depth of system installed

[tobnpr]

JAGSARE1 - 8/14/2006 12:28 PM

All risers and manifolds are RWC even if the engine is FWC. The block is FWC.

Not true.
Most have FWC manifolds. My 6.0 has FWC manifolds and risers- raw water is injected directly above the exhaust hose.

[OnaRampage]

I got 4 seasons out of my RWC manifolds and risers on a FWC engine. But that was with a good power washing cleaning in and out after 3 seasons. So I guess the fourth season was a bonus (and luck).
You gotta replace them!

- glen

[chuck34]

lostmyedge,
You never answered, RWC or FWC? If full FWC, most likely your manifolds are just fine. If RWC, yes, you probably should replace.

[prockvoan]

JAGSARE1 - 8/14/2006 12:28 PM

All risers and manifolds are RWC even if the engine is FWC. The block is FWC.

Big wrong there.Look at mercruisers FWC ing system.Raw water after passing thru the heat exchanger,discharges out thru the risers.There is a blocking plate in between the exhaust manifolds and risers.Engine cooling passes thru the engine,exhaust manifolds and then thru the tubed heat exchanger.

[chuck34]

prockvoan,

There are a lot of engines that are 1/2 systems, meaning the block is FWC, but the manifold and risers are RWC. Personally, I never understood the reasoning behind a 1/2 system, but they are out there.

[lostmyedge]

Update.. The system is a complete RWC, raw water to block, and exhaust manifolds and risers. I have just ordered (online, got a great price) new exhaust manifolds, risers, gaskets, and thermostat.

I do have one more question that maybe someone can answer for me. In the lower rubber boot after the riser elbow there is what looks to be a Flapper of some sort. It is mounted to a little metal bar that is in the lower elbow. Anybody know what that is for?

[chuck34]

Keeps water from backing up into the riser.