Exhaust Riser: quick fix and permanent fix options

[Wotname]

Originally Posted by jimbunyard

Thought it was clear...raw water, you can put your hand on it under load.

Not to the amateur pedantic mechanic

Ok so it raw water before passage though the engine or the discharged raw water?

[jimbunyard]

Originally Posted by Wotname

Not to the amateur pedantic mechanic

Ok so it's raw water before passage though the engine or the discharged raw water?

Last cooling duty before passing into the vented loop and thence the muffler.

This was for a H/E engine, discharged raw water after that component.

[wyb2]

Hi guys. Thanks for the replies. I had a whole response typed up to specific posts, then got a connection error while trying to post and lost it all. At anchor in the BVIs so connection can be finicky.

Tested my ad-hoc repair this morning and it does hold exhaust pressure. Planning to head to St Martin tomorrow, should be able to only run the engine long enough to set the anchor when we get there. My understanding is that's a better location to work on this sort of stuff anyways.

My main complaint with the design was the fiberglass wrap, not the iron pipe per say. Not only did removing it create a royal mess, it hid (and possibly accelerated) the corrosion on the pipe that, if noticed, would have had me thinking about replacement a while ago (before it rotted through completely). Like I said, the pipe rotted from the outside in, the inside was coated with soot but had no noticeable rust scaling.

But based on available materials I may end up replacing like with like, we'll see.

Thanks again.

[kmacdonald]

A black iron return bend is the cleanest way to do it. https://www.zoro.com/anvil-open-retu...07/i/G3173755/

Add a wye for water injection on the downside leading to the waterlift. https://www.zoro.com/anvil-wye-black...02/i/G0283367/

Use black iron pipe nipples to connect it all together. You might be able to find those fittings cheaper elsewhere, I didn't shop for best pricing.

[Aloha_float]

I have read numerous threads where universal engines have been outfitted with cast iron elbows that have been rigged to take the water mix into the exhaust stream. They fail prematurely. My universal 5424 had this configuration and it failed last summer. Westerbeke/universal have a proper aluminum casting mixing elbow to replace the home made crap elbows. I replaced mine last summer. Make sure you use the Teflon based goop on the threads so it does not seize on the threads if you ever have to service it.

[wyb2]

So just to wrap this up, I did end up replacing the dry section of exhaust with standard galvanized pipe. The prefab or custom stainless units look like good options, but we are actively travelling and galv pipe was available locally. Our existing setup already had the cast aluminum mixing elbow, and although a pitted, that looked like it had quite a bit of life left in it, so I reused it.

My big complaint was the fiberglass tape insulation that seemed to encourage corrosion of the pipe, and made an incredible mess in the removal process. I was able to find new wrap in St Martin, but was disappointed that it was giving off almost as many loose airborne fibers as the old stuff. What I ended up doing was fabricating a heat shield out of aluminum flashing and pop rivets. I forgot to take pictures, but I'll try to remember next time I have the engine compartment opened up. So far the highest I've measured with the IR thermometer was 135 F near the headers and 105 F near the mixing elbow.

[Farlander]

The wrap is there not to reduce heat in engine room but to increase heat in muffler to prevent soot buildup. At 1500 degrees F the soot doesn't accumulate but at 450F you will clog your exhaust eventually where the water mixes in.

[Searles]

If that copper tube bound exhaust has a meter or more of copper tube it will need on I’d of 1/2 inch or better still 3/4 I’d to avoid high back pressure due to internal friction ,verry hard on s/w coolant pumps ,the bigger the exhaust dry pipe the better ,but it does work ,sort of .⛵️⚓️

[wyb2]

Oh man, I remember this project. So this was 3.5 years ago, we've since moved back to land and sold the boat (always the plan).

I'd be interested to see an example of the too-cold exhaust gases causing a clog in the exhaust. I can see the logic, but the headers on this engine literally pass through the coolant reservoir, so it seems like Universal/Westerbeke wasn't too worried about keeping the exhaust temps up. Also, if my DIY heat shield is keeping cabin temps roughly the same as the fiberglass tape, then I think almost by definition, it is also keeping exhaust gas temps roughly the same.

Since I have real internet now, here are some pictures of the problem/fix. Unfortunately looks like I didn't get any pictures of the DIY heat shield, but it's basically a small box of aluminum flashing that clamps around the exhaust pipe with maybe a 1/2" air gap and covers the same areas that were covered by the fiberglass tape.



Pipe wasn't cracked or holed, it was completely severed into 2 halves with maybe an 1/8" gap between them. The fiberglass tape was the only thing containing the exhaust pressure (which is to say, it wasn't).


Literally duct table and bailing wire. It did leak, but dramatically cut down on the amount of exhaust entering the cabin. Allowed us to run the engine for 5 min at a time without fear of starting a fire.


New pipe assembled prior to install.