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Old 16-07-2011, 17:56   #1
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How High Can a Water Lift Muffler Lift the Water ?

because i anticipate losing several inches of waterline when loaded down for cruising i have taken the opportunity to raise my exhaust outlet, it was previously about an inch above the waterline and was a fiberglassed tube built the hull and the rubber hose slipped over the inboard side, im patching and fairing this and opting for a bronze through hull installed higher on the hull, id like to go as high as reasonably acceptable. The question is how high will the exhaust force the water out? how about adding a "stack" with the mixing elbow above the waterline and omiting the muffler, i bench tested the motor with only 3' of hose on the exhaust and was very surprised at how quiet it was with no muffler.
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Old 16-07-2011, 18:30   #2
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Re: how high can a water lift muffler lift the water?

The more important question is how much back pressure is allowed by the engine manufacturer. Your engine will reach the maximum allowable back pressure before it reaches its maximum ability to push the water up and overboard.

You probably want to call your engine manufacturer and describe your situation.
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Old 16-07-2011, 20:59   #3
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Re: How High Can a Water Lift Muffler Lift the Water ?

Oh my.. pls. don't experiment with this because you can flood your engine before you know it. Also, the fiberglass pipe is superior to a bronze fitting. Centek sells it.

ciao!
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Old 16-07-2011, 23:52   #4
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Re: How High Can a Water Lift Muffler Lift the Water ?

In many typical exhaust systems the water lift sends the water up to a high spot where it then slopes down gradually until being discharged.
As David says the back pressure can be an issue, but typically it is the height from the water lift to the "high spot". If by raising the discharge it becomes higher than the higher spot than the pressure may be effected.
As Nick says, you can flood your engine, this really sucks.
The vertical distances of the various components in the exhaust system verses the waterline, are critical......, and don't imagine that the manufacturer got it right to start with.
When I re-powered I went on an extensive learning spree to to engineer my new system.
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Old 17-07-2011, 06:54   #5
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Re: How High Can a Water Lift Muffler Lift the Water ?

See
Dave Gerr’s diagram from “Exhaust System Fundamentals”
Exhaust System Fundamentals ~ by Dave Gerr - Part 1 = 10 pages Part 2 = 12 pages Dave Gerr is director of the Westlawn Institute of Marine Technology, a practicing Yacht Designer, and noted author of: "The... Cruisers & Sailing Photo Gallery

And
The Northern Lights article, “Please Don’t Drown Me”
http://www.northern-lights.com/PDFs/...t_drown_me.pdf

http : //www . northern-lights.com/PDFs/misc_pdfs/dont_drown_me.pdf
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Old 17-07-2011, 09:31   #6
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Re: How High Can a Water Lift Muffler Lift the Water ?

Quote:
Originally Posted by GordMay View Post
See[...]
Where would we be without Gord... I could not think of where to start to come up with a link to that "Don't drown me" document

ciao!
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Old 17-07-2011, 09:50   #7
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Re: How High Can a Water Lift Muffler Lift the Water ?

Quote:
Originally Posted by s/v Jedi View Post
... I could not think of where to start to come up with a link to that "Don't drown me" document
ciao!
Nick.
It's been cited in about a half dozen different CF threads.
(thanx)
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Old 17-07-2011, 20:37   #8
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Re: How High Can a Water Lift Muffler Lift the Water ?

here is a picture of the situation, the upper hole is the exhaust (only about an inch higher than the old waterline) I understand the risk of flooding the engine but feel it needs to be re-engineered for offshore use.
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