Exhaust System Design

[REBrueckner]

I am posting this mostly for people who may be reconsidering a repower, but owners/operators with wet risers might also take note of the author's comments regarding such designs.

Some years ago I posted my own preference for insulated dry risers, after I discovered them
associated with my own 8v71TI's at the time and I recall a few comments posted regarding the pros and cons.

I came across what appears to be an excellent website discussing marine exhaust systems:

http://www.sbmar.com/articles/designing_a_marine_exhaust_system/

In the current case, we are evaluating an existing custom designed underwater exhaust systemfor a 1961 63ft Burger MY in which a naval architect has been engaged to evaluate some water intrusion. I found the illustrations and recommendations in the above website very helpful in developing questions for the naval architect.

 

[BOATER BOB]

Came across that last year and it was very helpful when I built my exhaust for my repower got the 316 90 degree ells and 316 tubing off amazon.
Bob

 

[sgharford]

Great article - thanks for sharing. Got me thinking I should replace my 40 year old wet risers (and count my blessings). Interesting tidbit that boat lift operator should always lift the bow first and let it sit for a few minutes to drain exhaust system (including mufflers), otherwise risk sitting water sloshing back up into engine.

 

[Maynard Rupp]

The risers and elbows on our Crusader engines was fabricated from a copper/nickel alloy that is the same as Crusader used for the heat exchangers. I can't find any good reason not to use this material for all the seawater carrying components of an exhaust system. Ours is lasting very well.

 

[sgharford]

I am torn with replacing mine, which appear to be original (going on 40 years old). They too are made of monel, or some copper/nickel alloy. They do 'appear' to be ok, all the welds look solid and I don't see anything funky regarding corrosion on pipe surfaces that are visible. I just replaced turbos and it would break my heart/boating spirit if they did start leaking as they are wet lined. New ones are close to 5 boat bucks, but new engines are simply out of the question (she'd become a live aboard for someone if catastrophic engine failure happens).

I love this site because ignorance is never an excuse and the article Rob posted gives valid reasons why wet liners are bad, which makes we want go ahead with new ones designed 'properly' with shower heads welded on ends and insulated with a blanket. At same time, knowledge can be disheartening when the only purpose of a pleasure boat is to bring joy. 40 year old risers sounds like a real anomaly.

 

[drburke]

Tony Athens is famous on BoatDiesel, and an all-around good guy. He is the West Coast guru of repowers; I have seen some of his handywork and sold him some engines.

His website is worthy of a read in general, and Cummins owners should check out the sbmar replacement raw water pumps (mentioned on the forum occasionally).

DAN