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Old 29-10-2008, 09:02   #1
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High riser exhaust

I’ve finishes the new exhaust system.


I'm had trouble conforming to normal practices with my exhaust layout/dimensions.
My engine manufacturer recommended no more than a 40" rise of the exhaust due to back pressure.
Given my configuration I would have to lift the water lift up so high that I would not have a safe distance between it and the engine exhaust.

I extend my exhaust dry stack up about 3 ft +(behind my companionway ladder) do a "U" bend at the top, then inject the cooling water into a sleeved piece of pipe,
then straight down with hose into the top of a water lift...this I fabricated out of a 10" dia fiberglass cylinder on its side. (left over from my bow thruster) and glassed in a nipple of FG pipe with 3” female pipe threads, then threaded into it a SS barbed fitting to attach the hose to.
The outlet is similar except the FG pipe extends down to with in an inch and a half from the bottom of the cylinder.
The outlet hose goes up to high spot (but lower than the dry stack) then slopes down until it exits the boat about 6" above the water line.

This is all pretty normal except for the extra high dry stack.
It seems that with the ”down stream” high spot being lower than the dry stack that it would be almost impossible to ever flood my engine. I also put a valve on the bottom of the water lift so I can drain it.
So far, so good
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Old 29-10-2008, 12:31   #2
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Aloha James,
This looks like a nice clean installation. How much higher is your dry stack than the 40" that is recommended?
JohnL
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Old 30-10-2008, 01:47   #3
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Thanks John.
The 40” I’m not to exceed is the lift of the water from the bottom of the water lift/lock to the loop, before exiting the hull.
The riser you see in the picture is dry going up (the white bit) then wet only after the injection point on the way down, that means that the exhaust pressure is not pushing any water up this bit.
The distance up from the bottom of the water lift to the top of my loop (the close-up picture of the double bend) is now less than 40”….but more importantly its also lower than the dry exhaust (riser) coming off the engine by about 9”.
In theory I could crank the engine until the cows come home and never back flood it.
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