'74 E29 Standpipe Muffler Build?

[justin.shay2]

Hi All,

I've been lurking on these forums since I bought my '74 E29 "Condor" in July of '22, but I have to run something by y'all in case I'm doing something crazy.

After removing, rebuilding, and reinstalling my A4, I found my existing exhaust standpipe (riser?) inner pipe is rotted out (see pictures attached.) With several recent improvements to raw water flow, I'm concerned that the inner pipe for the gaseous exhaust is rotted down to the point that the water exhaust will not be forced out to the transom, and instead follow the path of least resistance back to the manifold.

As much as I would love to buy the $775 MMI stainless replacement, it simply isn't in the budget after rebuilding most of the engine. I'm faced with essentially two options - move to a bunch of pipes that elevates the gaseous exhaust above the waterline before being injected with the water & running to a water lift muffler, or try to build my own standpipe muffler. I'm leaning towards building my own standpipe out of steel to save on costs.

I've attached a diagram I found on OldMarineEngine linked here, and a rough diagram of what I'm thinking on building. It would essentially be a straight pipe of 1 1/4" running straight up, then a 1 1/4" - 3" reducer welded to a 3" pipe that would provide the outer shell for the water to be injected near the base. I'd then weld a cap onto the top of the 3" pipe, leaving a gap for the gas exhaust to provide some pressure to prevent the water from backflowing into the manifold, instead being forced out the 1 1/4" pipe angled down to the transom.

Can anybody tell me if I'm being crazy here? Any tips or concerns?

Thanks all

Justin

 

[G Kiba]

I have heard really good things about Moyer Marine for A4 parts.

Search Results for “exhaust” – moyermarine

moyermarine.com

 

[G Kiba]

Sorry, I didn't recognize your MMI reference. Looks like you have been there.

 

[alcodiesel]

I had one built (out of SS) to the dimensions on the 3rd drawing- exactly like the old one which has never caused a problem, except rust out.

 

[justin.shay2]

Awesome, thanks for the replies. After a lot of toying around, I'm just replacing the inner pipe for now. The outer housing has superficial rust, but is cleaning up easily & is pretty uniform all around. I cut out the 1 1/4 pipe from the bottom of the larger housing and will be welding in a new 1 1/4 pipe to the specs in the drawing from Bill. I can see building & welding a whole new riser in the coming years, but I'll share results after the weekend.

Thanks all

 

[reginaldobaker]

Right on Justin, best of luck with the project. Any chance you could share the welding process and filler metal you plan to use? Just curious on considerations or tradeoffs if there are any (found it interesting the attached plans mention silver brazing). am planning to build a new standpipe for an E27 at some point and this thread has been illuminating.
Cheers

 

[justin.shay2]

Thanks, I ended up deciding that I was a little out of my depth with the metal work and brought it to a welder who took care of it for $80. I'm not certain about the silver brazing / tradeoffs, but I ended up going all steel.

1. He cut the 1 1/4 pipe weld off as close as he could to the cap without grinding away at the cap itself.
2. Torched the inner pipe and pulled it inward with pliers to break it loose from the cap (seen in the attached picture, the metal folded inward)
3. MIG welded with steel wire. The original was all steel, so he went with a new steel inner with steel filler. Stainless steel would last longer, but I figure steel has lasted 50 years, it'll last 50 more!
4. The welder also indicated that the outer section was all in good shape. While he cleaned the inside, he rammed a rod into the other cap a bunch to check that it wasn't about to blow out, and was ready to replace it if it was. It held up just fine.

The original was just heavily stick welded on, and there was no issue with that connection. I'm sure that stick welding would do the trick. It's pretty startling how rotten the inner pipe was - the attached photos show how far it had worn down. There were larger broken pieces that were pulled out separately, but it must've been holding on by a thread. Glad I caught it before it caused an issue!

Hope this helps with your process!

Justin

 

[reginaldobaker]

Awesome you got it taken care of so quickly. Very much appreciate the data points - these standpipes seem somewhat rare outside the Ericson sphere and are tough to find information for.