How to pressure or leak test water jacketed exhaust
 

Hi All,

Getting ever closer to starting this engine up for the first time in over 20 years.
I knew there was a breach in the short hot section of exhaust immediately aft of the manifold flange, and the copper water jacketed exhaust, while it looked OK, certainly needed close inspection and testing.
The first task was to see if I could even get the thing out of the boat in tact.
Success.
Attached are some photos.
I'll need a new exhaust flange for sure.
Whether I reuse this copper water jacketed system or refit with a water lift type unit will depend on the health of the copper water jacketed system.
From what I've read this type of system is very good and provides for minimum back pressure and very limited opportunity to water to syphon back into the engine. If I can reuse it I would like to.
My questions are, how do I effectively leak test and or pressure test the system?
Don mentioned somewhere about holding 20-30 psi in the water jacket for an hour or two. Someone else mentioned not pressure testing more than a few psi if at all and to leak test instead.
What is the best procedure?
Also, the copper I can see (obviously not the inside) all looks really fine except for maybe a bit of evidence of a leak (minor green corrosion) on the end cap at the aft end. Could JB Weld or MarineTex be a reasonable patch for this if there is a leak?
Thanks for the help.
Also

Looking at your pictures, I can see how the two pieces fit together, but WHAT is that gate valve for???

I think the benefits are as you've stated, with the trade off that it's big, heavy, and unwieldy. But, essentially no back pressure, and very difficult to get water back into the manifold - avoiding the 'keep the raw water intake off until start' directive.

I personally would not 'pressure' test. 20 PSI (most city water is at least 40 PSI) is a lot of pressure on an old copper manifold, and you'd just as likely blow out a joint as test anything.

I would leak test - put water into the water inlet, with a minor restriction at the outlet, and check to see that the exhaust part stays dry and water doesn't exit the jacket anywhere else. With the older cast iron sections on the output, visually check for corrosion. You have a late re-injection of water into the exhaust, and I'd always be a little worried about corrosion in that longer, still warm, cast iron (or is it still copper?) pipe section.

If you don't have one yet, get a CO monitor before you re-install into the boat.

What is this engine in. That is allot of hardware for a sailboat!! Perhaps you should snap a few pics of the area where that engine goes into. Looks like it was a straight run and they had a valve to dump exhaust water rather than have it go back into the engine.

Thanks Jeff. I've wondered about that gate valve also.
When installed it is situated at the very bottom of the system...on the exhaust portion. My only guess is that it is there to drain any water out of the exhaust portion in the event of water packing in from the back of the system, such as a huge following sea or something. Also, if there is so much MMO from storage that gets pushed out the exhaust, this would be a means to drain it out. These are my guesses anyway.
The aft section is also heavy gauge copper. It really looks good.
There was also some funky rubber muffler flange between it and the thru hull exiting the transom. Should have took a picture of it. It's labeled 'Mini Muffler'. Seemed to serve as sort of a flexible coupling between the rigid exhaust and thru hull, and had flapper fingers (best way to describe) inside.
Will work on some sort of mild pressure/leak test.

I was in the camp of advocating lower test pressures, a camp of one if I recall. My position was the water jacket of an iron engine with 40 years of salt water flowing inside would certainly be thinner than a new casting. How much thinner varies from engine to engine.

The goal of a pressure test is to check for breaches and if breached it won't hold even a low pressure. During operation a RWC engine has virtually zero internal pressure. Applying a higher pressure "just to see if she'll hold" risks destruction of the castings. You may create the breach you were hoping wasn't there. As the engine ages the risk increases.

Looking at the first picture, it looks like the flange itself may be OK, and what has failed is a pipe nipple between the flange & the "Y". I'd redesign this whole section and ditch the "Y" & the gate valve.

Your system is very much like the original one in my 1967 C&C Corvette...the gate valve is for draining condensate and water that is pushed into the exhaust by following seas - it also acts as a surge chamber.

I replaced my bronze system with an MMI waterlift exhaust - worth every penny!

:cool:

Thanks everyone. The boat that this was in is a C&C Corvette. A 31 ft. sloop.
I think a more diligent job of routing things could be accomplished so this wouldn't hog up the whole port lazarette.
The water jacketed section runs aft...more or less level at appx. waterline, then that other copper section joined via the union joint extends upwards under the aft deck and the cooling water injected in again on the downward slope and out the transom.
The flange is pretty much toast. I actually had a spare stainless steel one from my Palmer, but just my luck, the bolt holes are slightly different.
I believe if this unit checks out OK, I can remake the flange/nipple section and simply reinstall as is with only a little modification to tidy things up.
I've come to like the idea of the large gate valve at the bottom of the system.
What better way to check for a leak in your internal water jacket than to occasionally open that gate valve and see if any water comes out?
Any opinion out there on using JB Weld or MarineTex to patch any pin holes found on the end caps?

If I was on an extended trip and didn't want to haul out the boat I would say give it a go...but IMO the only way to plug those is brazing/silver solder.

One of the reasons I went with the MMI water lift was to get back some of that lost space in the port lazarette...I also used an in-line stainless steel swinging check valve to stop incoming/following seas from flooding the wet section of the exhaust.

:cool: