Exhaust risers

What is the purpose of risers 4 and 8 inch? My boats application does not have these. I only have the log style manifolds then directly to elbows.
Thanks
Jim

The risers are available in the case where the engine is installed 'low' relative to the water line and there isn't enough 'slope' to keep the water out of the exhaust tube. you can find the install manual on the Crusader www site if you wanna read up on how to make the determination of the need for risers.

makomark said:

The risers are available in the case where the engine is installed 'low' relative to the water line and there isn't enough 'slope' to keep the water out of the exhaust tube. you can find the install manual on the Crusader www site if you wanna read up on how to make the determination of the need for risers.

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How much slope is needed?

jclays said:

How much slope is needed?

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Ayuh,..... The distance from the water level, outside the boat, to the point where the exhaust turns in the elbow has to be 13" or more,......

maybe this will help:

makomark said:

maybe this will help:

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I read this on Crusaders site yesterday. What is point A. Is it the deck or the top of the gunnel? Even if I needed risers they wouldn’t fit anyway. There’s only 2 inches between the top of the elbows and the bottom of the deck. So that’s why I’m more concerned with rise and run. This is how she’s been since built in 1966. This caused an issue when I lost the front muffler mount dropping the front of the muffler allowing water to pool and letting the engine suck in the water..that’s the reason for new engine.

There is no Point A. measurement A is from the waterline to a reference point, usually the deck. Measurement B is from the riser top to the reference (deck).

makomark said:

There is no Point A. measurement A is from the waterline to a reference point, usually the deck.
Measurement B is from the riser top to the reference (deck).

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As Mark said, A and B are dimensions only.

B dimension is actually from the top of the Elbow to the reference point.
The Riser/Spacer (if equipped) sits underneath the elbow.
In order to raise the Elbow, a spacer/riser would be added.



I know..... I know...... it's my pet peeve when it comes to Elbow vs Riser/Spacer!