How to test exhaust system

[ajgaines]

My current engine was ruined by flooded water. I think it was the previous owners cranking with the seacock open. I am thinking of buying a rebuilt engine from moyer, but am terrified it is an issue in the exhaust. Does anyone know how I can properly test the exhaust system to make sure that it's not a blockage in the exhaust system? There doesn't seem to be guidance on this in the manual

Cheers!

[jcwright]

Hello ajgaines.

Below is a comment from Don Moyer on back pressure, from a 2011 thread on a similar issue. Perhaps this is of some help with your situation.

best regards,

jack.

Moyer's comment:

"The Atomic 4 likes a quite low exhaust back pressure of 1 to 1-¼ psi. Our tech service experience indicates that much of the Atomic 4 fleet (my guess would be at least 70%) is suffering some impairment in performance or reliability due to some amount of elevated exhaust backpressure. Symptoms include chronic sootiness of all four spark plugs, one or two cylinders failing to work with otherwise good compression, engine refusing to accelerate accompanied by a “gagging” sound from the carburetor, engine running better with any one of the four plug leads removed (yes, believe it or not), and eventually failing to start.

Being able to read your exhaust back pressure won’t in and of itself cure the problem but given the difficulty of working on the exhaust system, it would be good to know before starting that gruesome work that you do indeed have a blockage. Difficult access on some boats can make even this suggestion a bit difficult, but the reward will be worth the effort.

In the event that you can remove the two bolts retaining the exhaust flange, some folks have diagnosed elevated back pressure by removing the bolts, propping the flange away from the manifold a fraction of an inch and running the engine for a few seconds. If your symptoms are quite profound, you should notice a definite improvement in running for just a few seconds.

If you can remove the two flange bolts, you may also be able to remove the entire hot section of the exhaust and replace it as a preventative maintenance measure without ever testing the back pressure."

[ajgaines]

Thanks for the reply, however, my engine is out and I want to just buy and install a rebuilt one, is there any way to test the system like that? Looking into the waterlift it does not look as if it's full of water, squeezing the flexible tube after the waterlift it doesn't seem as if there's any hard blockages but I don't think that's the best way to tell..

[ndutton]

The prescribed test is as JC described on a running engine. Beyond that you're left to your own imagination. A possibility might be with a long flexible borescope/endoscope such as the one described here:

http://www.moyermarineforum.com/forums/showpost.php?p=109135&postcount=1

[ajgaines]

I like the idea. The two things I tried was blowing in it haha and running a coat hanger just to see if there was general stuff stuck in there. Didn't really get anywhere with either one. But here is the waterlift. Where the engine enters is a little weird. Maybe the previous owners just made their own little fiberglass fix to it cracking or something? Or is this normal? It looks a little restricted at the point of entry

[ndutton]

Do it right, cry once

Your waterlift is the proprietary Catalina model, early (problematic) version. Catalina Direct has a newer direct replacement model although at their price it must be gold plated. This link discusses your exact problem:

https://www.catalinadirect.com/shop-by-boat/catalina-30/engine/exhaust-system/aqua-lift-muffler-c-30/

There are other options, all of which have been used successfully by forum members:

http://www.moyermarineforum.com/forums/showpost.php?p=103136&postcount=2

[zellerj]

I had a muffler like that about 18 years ago. Then one autumn I got the bright idea to winterize the engine by recirculating antifreeze from a bucket. To do this I place the hose from the through hull in a 5 gallon pail of antifreeze, and took off the exhaust injection hose from the exhaust fitting and ran the engine for a few minutes. I was pretty proud of myself until the next spring when I found that the fiberglass Catalina muffler was leaking. Upon inspection the muffler had a collapse inlet, and looked like yours, because of the non-cooled very hot exhaust running through the muffler inlet.

I replaced it with a cheapo Vetus that allowed me to get up and running with no other modifications. Didn't think my Vetus would last 18 years, but it has. Since the volume is less than other options, I am particularly cognizant of how long my engine takes to start.

If you are looking for exhaust blockages, sometimes it is caused by old collapsed exhaust hose. The hose can look fine from the outside, but the inner liner is collapsed. Have fun checking this out.

[ajgaines]

I'm thinking I should just replace the whole exhaust hose and water lift then?

[ajgaines]

Is there a way for me to fix the muffle I have now? Like take a 1.25" stainless tube and fiberglass it to the current fiberglass?

[ndutton]

The water lift has already failed at least once, a repair has been attempted and it has failed too exactly as shown in the Catalina Direct link I posted earlier so it’s my opinion another repair attempt is ill advised. Please notice the title of my previous post (#6).

As for whether or not to replace the entire exhaust hose, there is no harm in doing so but I don’t think it’s necessary unless you have evidence of a problem such as excessive exhaust back pressure or visual endoscopic evidence.

[jcwright]

Hello ajgaines.

I hesitate to give advice to anyone on how to prioritize work on his or her boat. A compromise that's acceptable to one person might give nightmares to another.

But since you ask for people's thoughts on this, here's my 2c worth. Installing a rebuilt engine is major investment of time and energy, at least it was for me. While the old engine is out, you will have a rare opportunity to attend to things that will be more difficult to do later. Plus, there is the risk that the existing waterlift is ready to retire. So, in this situation my sense is that there is wisdom in the "cry once" philosophy that Neil mentions.

Best regards,

Jack