Gaining exhaust height with a dry riser

BillD

Admiral
Joined
Sep 1, 2011
Posts
8,138
Likes
3,890
Location
Portsmouth NH.. Piscataqua and Merrimack Rivers
Boat Make
27 H&H with Cummins QSB 5.9 480 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

Captain
Joined
Jul 24, 2012
Posts
664
Likes
295
Location
Litchfield, CT / Punta Gorda, Fl
Boat Make
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
 


Top Bottom