New Exhaust

Thomv

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Feb 26, 2005
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I just picked up two sets of exhaust manifolds and risers for my 454 MerCruiser engines. I have a question concerning the gaskets that go between the exhaust manifold and riser. There are two kinds of gaskets. I am not sure what gasket to use for my exhaust. One set has some of the water passages blocked off while the other set has all the openings for the water flow. I mostly use my boat in salt water. Which set of gaskets am I supposed to use? The ones with all the water passages open or the set with some of the water passages blocked off? If I am not clear I could attach some photos of each type of gasket.
 

alldodge

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I just picked up two sets of exhaust manifolds and risers for my 454 MerCruiser engines. I have a question concerning the gaskets that go between the exhaust manifold and riser. There are two kinds of gaskets. I am not sure what gasket to use for my exhaust. One set has some of the water passages blocked off while the other set has all the openings for the water flow. I mostly use my boat in salt water. Which set of gaskets am I supposed to use? The ones with all the water passages open or the set with some of the water passages blocked off? If I am not clear I could attach some photos of each type of gasket.

Since you have open cooling and do not have risers, you would use part number 863724 gasket (item 8). This has just the two holes, one on each side
Exhaust.jpg
 

Thomv

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Feb 26, 2005
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244
Thanks for clearing this up for me. So a riser would be something you would put between the exhaust manifold and the exhaust elbow to raise the height of the exhaust elbow if needed to run the exhaust out the back of the transom? Yes?
 

alldodge

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Thanks for clearing this up for me. So a riser would be something you would put between the exhaust manifold and the exhaust elbow to raise the height of the exhaust elbow if needed to run the exhaust out the back of the transom? Yes?

The riser is used in most cases the raise the height of the exhaust based on how low the engine sits. Many boats sit high enough to keep from having water ingested during a fast stop. Those that don't risers are installed between the manifold and elbow to help. Since your boat did not come with them, Power Quest determined they were not needed.

You should have exhaust flappers installed to help stop the water
 

Bondo

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Thanks for clearing this up for me. So a riser would be something you would put between the exhaust manifold and the exhaust elbow to raise the height of the exhaust elbow if needed to run the exhaust out the back of the transom? Yes?

Nope,.... Nothin' to do with thru-hull exhaust,....

As AD says, it's 'bout how deep the motor sets in the hull,....
The tip-over point of the exhaust in the elbow has to be atleast 13" above the outside the hull water level,.....

Common lingo, which I'm very guilty of,... calls what the parts books say are elbows, Risers,.....
The cast iron blocks this topic is 'bout, I'd call Riser Blocks or extension blocks,.......
When I'm readin' elbows in the context of posts here, I'm seein' the pipes that tip-over into the y-pipe,....

A google seach of SSteel elbows won't find ya much for aftermarket shiny parts that bolt on top of exhaust manifolds,....
But a search for SSteel Risers will find 'em,....
 
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