Exhaust Elbow Doomed?

[Jerome Billett]

I’ve posted this question before about different boats/engines but this is another and I’m still not sure what to look for exactly.
1998 Jefferson 48. Volvo 72P-A motors. 430 HP. The raw water entrance to the elbow is high but sort of slopes down. Still doomed to fail?
Also, anybody know what the P-A refers to on these engines? There is no throttle cable attached to the fuel pump lever arm so I presume there is an electronic control somewhere. Any ideas?

Topic

[Jerome Billett]

That sounds pretty reasonable. Certainly better than the jacketed doomed to fail ones that cost about $4500 from Cummins the last time I checked. Thanks again for all the good advice.

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Corey Schmidt

[Corey Schmidt]

Without knowing ALL of the little details about the project, it’s difficult to say but you’d be pretty safe figuring somewhere around $3k per side for all the labor, materials, etc. to have custom exhaust fabricated…

[Jerome Billett]

Corey,
Thanks again for helping me assess this Volvo engine exhaust design. I have read pretty well all the Tony’s Tips on the exhaust issue and you have confirmed for me that all these “deAngelo” style double walled elbows, while nice to look at and easy to fit are doomed. I guess the only way to rationalize it when buying a boat with this setup is to accept that a new exhaust system has to be installed. In the pictures you provided, can you give me a ballpark number on cost per side for that design?
Regarding the throttles electronic vs. manual, I am not where the boat is situated any more so cannot get the info you require. We will have to leave that for now.

[Corey Schmidt]

Re: the throttle control, send in some pictures of where everything on the throttle circuit connects… control head, electronic modules, engine connection, etc. and we’ll see if we can sort out how the engine is controlled…

[Corey Schmidt]

After looking at all of your pictures… here’s the “skinny”

Those factory mixers are known for rotting through… just is what it is (bad materials, bad design, etc.?) They ALL do… the water that comes in to the elbow comes into STRAIGHT DOWN and erodes the inner jacket… where the water goes after that, nobody knows…

Only real LONG TERM alternative is to fabricate a SAFE custom exhaust riser that leverages the available height that you have in the engine compartment and that injects water into the mixing elbow both on the the down hill run and at the proper orientation…

https://www.sbmar.com/articles/typical-properly-designed-marine-port-starboard-exhaust-risers/

[Jerome Billett]

Thanks again Corey. There is what I assume to be a muffler. See the YW listing here. There are photos of the mufflers. Maybe you can figure it out.
https://www.yachtworld.com/boats/1998/Jefferson-48-Rivanna-3204386/Jacksonville/FL/United-States?refSource=standard%20listing#.WzlyyNJKiUl
I don’t know about the ECM. All I can tell is that the throttle cables terminate at some sort of electronic module under the dash at the helm and I cannot see any throttle cables attached to the engines. The gauges are all analog with no display for fuel economy, or anything. I need someone who knows about these things to explain it to me.

[Corey Schmidt]

18″ of clearance above the water line is probably enough but it still depends on a few factors… is there a muffler involved in the exhaust loop before the water exits the boat?

Re: the throttle input…. are these ECM controlled engines or are they mechanical?

[Jerome Billett]

Water level

Corey, thanks for the reply. I don’t know for sure but if I had to guess, judging by how I remember the position of the the deck drain overflow fittings, I think there would be about 18″ or more. It’s a big engine room.

[Corey Schmidt]

Do you know where the level water line is in relation to the center line of the turbo exhaust outlet?

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