Which Exhaust Riser to order from CD?

[captran]

Thanks Ron.  You would think there would be more consistency within models.  Oh well, so far, so good on mine.  I do smell maybe a little faint smell when I open up the engine but have not yet poked around  to get a better look.  Maybe in a few days after I finish the more pressing issues.  So far, just did the racor primary filer  R-15S and the transmission fluid change and ran the motor for about an hour total.

[Frasse Pelle]

Ah... nothing easy. I removed the muffler riser today and it looks like I got a 3 pieces nipple'd riser similar to CD part #Z3055 (see picture). But, I do measure the extension closer to 3 inch. So, should I go with Z3055 with 3.5inch extension or Z4491 with 2.5inch extension? Or it really doesn't matter and both will work?

please post or send me a message re which riser you get and why, as I have a 97.  also, did you have to replace the exhaust flange?  and how long for various things.  think I'll have to have mine done, as I can do basic stuff but this seems over my head.  thanks.

Hi Mark (Captran), I got the Z4491 with 2.5inch extension. Did the installation this morning without issues. I did change the flane as well.
Now moving my attention to the heat exchanger re-install. Always something.

[Ron Hill]

Francois : When you reinstall the HX just make sure that there isn't so much insolation that it presses against the exhaust riser.

A thought

[skyward]

recommendation from the survey was to change the Exhaust riser

Francois, thank you for starting this thread. Did the person performing the survey actually remove the exhaust riser insulation? I'm curious how they came to the conclusion you needed to replace it. I'm impressed that they made the recommendation which seemed correct based on your pictures. I think I wil do the same...we have similar vintage boats.

Anyone, I assume that the number one problem with these exhaust risers resulting in having to replace them is corrosion failure. Does anyone know why this is? Is there a galvanic corrosion issue designed into the system? Is that why we would replace with electropolished S/S?

[Stu Jackson]

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Anyone, I assume that the number one problem with these exhaust risers resulting in having to replace them is corrosion failure. Does anyone know why this is? Is there a galvanic corrosion issue designed into the system? Is that why we would replace with electropolished S/S?

Jeff,

I've removed my exhaust riser three times and replaced it twice in the 22 years I've owned our boat.  I've written two tech notes about it, the last one being this one in the February 2016 Mainsheet magazine:  https://c34.org/muffler-exhaust-riser-replacement-2015/

That tech note includes references to my earlier tech note and to Ron Hill's many contributions on the topic.

The answer is that the mixing of the exhaust gases and the seawater (raw water) that has passed through the heat exchanger is a CORROSIVE mix.  As in chemically corrosive.

You can use any material for the riser, and over the years there have been many choices skippers have used: from galvanized to ss.

Here's a link to a much older static 'site post:  https://www.c34.org/faq-pages/faq-exhaust-pipe.html

Your boat, your choice. 

[Frasse Pelle]

Hi Jeff,

This was reported by both the Engine Surveyor and the Marine Surveyor. Neither removed the insulation but they did find corrosion near the muffler. They might have pulled a bit the insulation at that end. But, both made it clear that this was a must do before using the engine for extended hours. so.. I essentially changed the Exhaust Riser, the heat exchanger and many cracked hoses. They engine has run smooth since.