Exhaust hose bad or not?

[jimesh]

The flexible exhaust hose from the waterlift muffler to the transom on my Pearson 35 (18' long!) shows small cracks all over, and has been pretty much like that since we've owned the boat (12 years). No evidence of exhaust fumes in the cabin or lockers until the exhaust hot section water injection area failed in September. The CO detector only went off when that happened. But while I'm redoing that (in SS this time!) I've been thinking about whether to replace that hose too at ~$350 or so. If it's not really bad and the cracks are only cosmetic, in the outer layer, then I'd rather not of course. Any ideas how to tell? I may leave it 'till the coming season, and cover a section of it with clear plastic and see what builds up there after some engine running time if there's no other way.

I'm also wondering about using the MMI hot wrap on the new 316 stainless steel hot section given its known ability to corrode just like iron when it doesn't have free access to oxygen. Some other threads here implied some issue with this. Looks like I'd have to cobble up a heat shield out of stainless sheet otherwise, not a lot of fun either.

[TimBSmith]

Wet side exhaust hose replacement..

Great to see your post. I went down this road in September. Just as soon as my engine started running (Yeah!) and producing more exhaust/water pressure the hot side and wet side of my Pearson 30 exhaust system showed their weak spots.

I learned that the wet marine exhaust hose has wire mesh and insulation material for heat and pressure protection. My marine exhaust hose had developed rot and stress cracking exactly where it was clamped to the stern exhaust fiberglass tube. The hose began leaking there and led me to investigate the entire run of marine exhaust hose in my boat (also nearly 13 feet). There were a few more cracks and much of it looked very serviceable. I put pressure on cracks where I could to see depth to wire mesh. Many cracks could not be tested without removing the entire run of hose. I bought some rubber exhaust system patching supplies. Then I thought again...

I decided that if I was worried enough to test or preventively patch cracks (which was evidence of a material's compromise) I should replace the marine exhaust and know that this critical system is not a failure risk. I read again and again from more experienced skippers that so often it is better to just get the financial pain out of the way quickly and simply know that risks are managed. Especially with critical systems. Happy Holidays. Stay well.

[JOHN COOKSON]

G
I decided that if I was worried enough to test or preventively patch cracks (which was evidence of a material's compromise) I should replace the marine exhaust and know that this critical system is not a failure risk.

Doubts are not a good thing to have when out on the water.
Exhaust hoses can delaminate on the inside and block the water\exhaust flow. If there is any question about the hose's integrity replace it.

ex TRUE GRIT

[Dave Neptune]

If the exhaust hose shows any cracks it means that the water has a chance to get into the wire and rust it out. The water can enter at one end and not look to bad BUT somewhere downstream (a low spot) the water will settle and do it's harm out of sight weakening the hose and the bond between the hose layers a bad thing. Also if the hose gets hot from lack of good water flow it can cause weakness and a delamination of layers.

Ten years is a good long life for an exhaust hose in salt water and maybe a bit longer in fresh water.

For safeties sake replace the hose if there are any doubts, worth the investment and labor.

Dave Neptune

[jimesh]

Thanks guys, good advice about some consequences I hadn't thought about. Time to tackle that.

[Surcouf]

What will fail first, and it is invisible, is the internal liner. When I removed my engine, I discovered that the internal liner had collapsed, and was creating a serious restriction to the exhaust flow (gases+water). Another user on this blog had the exact same issue recently.
I would strongly recommend to change it if it shows its age on the outside

OK I found my post from last spring

https://www.moyermarineforum.com/forums/showpost.php?p=121202&postcount=167