Designing and fabricating a custom exhaust

BillD

Admiral
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Portsmouth NH, boating out of the mighty Merrimack
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25 Terry Jason with Cummins 370 power
For the forum members interested I thought I'd share the "nuts and bolts" of designing and fabricating a SS exhaust system that will last the life of the boat with ZERO chance of sea water ever backing into an exhaust turbo.

These twin engine exhaust systems were built in CA using detailed measurements of the boat's engine/engine room supplied by the owner.

Important to note is that the exhaust fabrication shop NEVER looked @ the boat. This shop has supplied upwards of 60 + exhaust systems worldwide with ever seeing the boats in question.

The measurements "start" at the center of the exhaust turbo. Doesn't matter what color/make of engine, single or twin install or type/make of hull...all key measurements start at the turbo/s.

From the turbo the boat owner will measure height in inches to the bottom of the engine hatch/s, length to the rear engine bulkhead, lateral and height measurements from the turbo/s to the boat's exhaust exits through the rear engine bulkhead and finally the measurement in height from the water line of where the exhaust exits to the center of the turbo.

After a telephone call or two to "double/triple check" all owner supplied measurements and a few pics of the engine/boat install the work begins.

You'll see in the pics that a "mock up" engine room (overhead hatch and rear bulkhead) are used along with the an engine either in the boat or the one going in. From there the SS pieces are welded up and a proprietary SS shower head is made, fiberglass surge tubes and running lengths are glassed and coated. All hump hose, clamps are all supplied.

A "key" component to every exhaust system that leaves this shop is a 180F temp switch attached to each shower head. (a trained eye can see the switch on this install LOL).

This provides the owner the option (HIGHLY RECOMMENDED) to add a "loss of raw water cooling water" alarm to the engine. IMO it is the most important engine alarm you can have.

Here are the pics of the "shop mock up and exhaust pieces and the owner supplied final install pics. ALL fit like a glove. What's missing from the install pics are the customer heat wraps.

For what it's worth,

Bill D

Davids--Stb Mock up (2) (1).jpg

Davids--Stb Mock up (3).jpg

Davids--Stb Mock up (1).jpg
 

Hurdy Gurdy

Lieutenant Commander
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Sep 30, 2011
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BERMUDA!
This is very interesting Bill! Is the average length of a surge tube 12-14"or can it be longer.
 

BillD

Admiral
Joined
Sep 1, 2011
Posts
6,674
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Location
Portsmouth NH, boating out of the mighty Merrimack
Boat Make
25 Terry Jason with Cummins 370 power
This is very interesting Bill! Is the average length of a surge tube 12-14"or can it be longer.
Hurdy,

The surge tubes can be as long as needed to work. Obviously the tubes must fit the constraints of the boat.

Longer does not hurt, but it's always best to have the tubes rise as they go forward.

Also, as they get longer, the tubes may need additional support !

For what it's worth,

Bill D
 

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