Gaining exhaust height with a dry riser

BillD

Admiral
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Sep 1, 2011
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Portsmouth NH, boating out of the mighty Merrimack
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25 Terry Jason with Cummins 370 power
Here's a good example of a diligent boat owner recognizing that his engine exhaust was not "high enough" off the waterline to prevent a potential back wash slug of water into the turbo and engine.

Minimum height must be 12" to the spill over point on the turbo.
I'm unsure of the original height but the new exhaust being fabricated by Seaboard Marine Oxnard, CA provides 5 inches of extra height and a mixer that drains by gravity. You'll notice the original mixer on the Yanmar "held water".

FWIW,

Bill D

Marine_Exhaust_Height[1].jpg

Southern_Cross--Exhaust_(1)[1].jpg

SouthernCross_Yanmar_exhaust[1].JPG

Copy_of_2-_before_modification_(2)[1].JPG
 

djmarchand

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Jul 24, 2012
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Litchfield, CT / Punta Gorda, Fl
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Atlas Pompano 23 outboard
Another approach

That installation looks like it is on a Mainship Pilot 34. I totally agree that the original design was worthless: too low above the waterline and if the ijection elbow fails internally it will drain into the turbo.

I just finished a similar project for my Pilot 34. Here is a pic. I reused the original dry elbow and welded an 8" extension and another long radius elbow so the injection elbow would point downward.

I was concerned about back pressure as mine has much smaller dry exhaust diameter that the OP's. But it all worked fine and the engine spun up to rated rpm + 100 at wot.

David

Bella final exhaust system- small.jpg
 
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