what's all this I hear about bad manifolds

[KRS]

I have a 2.5L mercruiser from 1987.<br /><br />I read quite a bit on this forum about "riser" going bad and that allows water to enter the engine via the manifold, because water is in the manifold mixing with the exhaust, and something rusts out and causes the water to go where it shouldn't.<br /><br />Do I have the type of manifold that would allow this should a failure occur?<br /><br />I have never seen inside a manifold, so I really don't know what the issue is all about.<br /><br />Thanks.<br /><br />

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[Reel Poor]

Re: what's all this I hear about bad manifolds

Definately....And they are a lot cheaper than an engine replacement.

 

[KRS]

Re: what's all this I hear about bad manifolds

Hello Reel Poor... definitely what? Mine are the kind that go bad and ruin the engine?<br /><br />Thanks.

 

[Reel Poor]

Re: what's all this I hear about bad manifolds

KRS water is used to cool the hot exhaust manifold. They will eventually rust somewere to the point of failure. Typically they rust out where the riser and the manifold are bolted together. This allows water to drain into the dry part of the exhaust manifold and into the cylinders via the exhaust valves. This can happen with little or no warning. Boating in the salt pond we recommend changing manifolds and risers about every four years on raw water cooled engines. On the closed water cooling systems we recommend checking the risers every two to three years and replacing the risers if corrosion is evident. Looking at the pics you posted I would recommend some close inspection of your exhaust system. If they are origional they have served well. I would remove the riser/elbow for inspection. Rubber boots should also be plyable. If corosion is found they should be replaced.<br />Here is a pic Don S posted that shows the area that need to be checked.<br /><br />

<br /><br />Here is an exploded view of your manifold setup.<br /> <br />

<br /><br />Hope this helps.

 

[KRS]

Re: what's all this I hear about bad manifolds

It does, will bust loose those rusty bolts and check <br /><br />I figured that my picture #2 showed a large hollow elbow, I didn't figure that it bolted down on top of something like the picture you posted.<br /><br />Will check and post the pix.