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Old 05-26-2015, 01:28 AM   #1
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Failed Fiberglass Exhaust Coupler

6 inch fiberglass exhaust system coupler has fractured, leaking exhaust and water into bilge. It is a joint coupler between two rubber bellows. The rubber bellows are clamped to the fiberglass coupler with two standard hose clamps on each side of the bellows. I have a new coupler ordered. Does anyone know if a sealing material is spread on the fiberglass prior to assembly, or are the bellows simply clamped to the fiberglass? The old fiberglass coupler seems awfully rough on the surface for an effective seal.
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Old 05-26-2015, 06:56 AM   #2
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I just looked at mine and it appears the rubber bellows are simply clamped to the coupler. Why did the coupler break?
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Old 05-26-2015, 07:00 AM   #3
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These will be fire retardant GRP , and the usual failure is they got too hot .
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Old 05-26-2015, 08:10 AM   #4
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Yes, it got too hot. I would take a look at your raw water system for proper flow and the internals of the mixer for corrosion and plugging of the water holes.

You should be able to hold your hand on that fg piece at idle and under load. Are you making steam out the exhaust? Another indication of low flow.

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Old 05-26-2015, 10:33 AM   #5
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[QUOTE=CaptTPT;335838]It is a joint coupler between two rubber bellows.
QUOTE]

That sounds unusual to me, a piece of Fiberglass Pipe between two rubber bellows. Why would you have 2 rubber bellows in a row on an exhaust run? Are they single hump bellows?

Regardless, typically there is no sealant in these applications, none necessary. The Fiberglass pipe is available from Centek in a rather thin wall version, or other sources for a heavier wall (1/4" approx)

There are also s/s "crush rings" available for added strength for these applications.

As mentioned, the typical failure is due to water starvation as the working temperatures on fiberglass exhaust components is well above 150F and failure temps are +200F.

Did yours burn through or was it a mechanical failure (crushed?)

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Old 05-26-2015, 10:57 AM   #6
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Quote:
Originally Posted by djmarchand View Post
Yes, it got too hot. I would take a look at your raw water system for proper flow and the internals of the mixer for corrosion and plugging of the water holes.

You should be able to hold your hand on that fg piece at idle and under load. Are you making steam out the exhaust? Another indication of low flow.

David
Junction between bellows began dripping several months ago. Raw water impeller is new and water flow out exhaust appears normal. I frequently put an infrared temp sensor on exhaust. Never been hot to touch or by sensor. The more I tightened the clamps, the more it leaked. I initially thought the rubber bellows was fractured. I took the clamps off and pulled the bellows back. Found a straight smooth longitudinal fracture down the entire length of the fiberglass. Tightening simply separated the fracture more. This unit couples the bellows attached to the turbo outlet to another elbow bellows. 15 yrs old.
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Old 05-27-2015, 06:44 AM   #7
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Purchsase better hose clamps.

The spring tensioning type should keep you from crushing the new GRP piece.

Be sure its exhaust rated as regular GRP burns very well.
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Old 05-27-2015, 10:24 AM   #8
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Sounds like the clamps may have been progressively over-tightened to the point they cracked the fibreglass.
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Old 05-27-2015, 11:12 AM   #9
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Sounds like the clamps may have been progressively over-tightened to the point they cracked the fibreglass.
What do you do when you get a leak?? Tighten the clamps! Well thats what I did. It clearly worsened the problem. Next time I will do it different. Sleeve is $36. No big deal.
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Old 05-27-2015, 11:49 AM   #10
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I had a problem similar to this on my Hatteras. We installed crush rings on the new tube sections, and yes, we used a sealant, a very high temp Permatex, the exact model of which I forget. Among other benefits, it lessens the amount of clamp tightening required. This is not a system to take shortcuts on.




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Old 05-27-2015, 03:19 PM   #11
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Thanks for the info. I'll check out the crush rings and the Permatex.
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Old 05-27-2015, 07:19 PM   #12
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Quote:
Originally Posted by CaptTPT View Post
What do you do when you get a leak?? Tighten the clamps! Well thats what I did. It clearly worsened the problem. Next time I will do it different. Sleeve is $36. No big deal.
Well, not necessarily. If your "solution" is making the problem worse, it's time to stop. I had a similar problem at the water muffler, so do as I say, not as I did!

And that crush ring as shown by calflexflanc sounds good too.
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Old 05-27-2015, 08:42 PM   #13
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Half the failures are from being crushed by t-bolt clamps, the other half by heat.

T-bolt clamps put on an amazing amount of squeeze compared to worm screw clamps. Crush sleeves help. Or just be easy on the wrench!!

A bit of plumbers dope or rectorseal smeared on the FG pipe help fills little voids in the weave and cure the seepage that otherwise happens. Permatex would work too. Seen silicone RTV used with success. Anything sticky and gooey also, I suppose. Maybe peanut butter.
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Old 05-27-2015, 09:10 PM   #14
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Rescue Tape works too. I had a small crack/ooze on the Beast's muffler (Centek variety) and rescue tape solved that. Rescue Tape is one-part miracle.

Oh, and do not under any circumstances "save money" and buy an off brand. It's about half the price of Rescue Tape, and about half as thick. Plus, the roll I was given is not heat resistant to the degree that Rescue Tape is.

I'd given someone the rest of my Rescue Tape who had an issue with his stuffing box. As he was leaving the boat for a bit, the Rescue Tape eliminated the leak until he could get back and re-pack the gland. He didn't have any of that stuff either.

It was a new-to-him boat. And the "rescue tape" he bought sucked bilge water. It didn't appear to adhere as well as the real stuff either.

Since then I've bought another roll. It's about $10 on Amazon. Get clear so you can see through it.
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Old 05-27-2015, 09:23 PM   #15
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I should note that the crush rings were $ealed in u$ing the $ame very $pecial high temp epoxy that was used to attache the new tubes to the mufflers. yes it turned out I had the same problem developed or developing on both sides. Fortunately we were in an area with a lot of builders of big boats; we got the crush rings from Hatteras and the epoxy through one of the custom guys. I would say that if you were just doing tube to hose connections, one of the high temp sealants would work, but you have to seal those rings well; there's salt water running through there and you do not want crevice corrosion.
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Old 05-28-2015, 01:01 AM   #16
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Thanks for the info
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Old 05-28-2015, 07:20 AM   #17
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Quote:
Originally Posted by janice142 View Post
Rescue Tape works too. I had a small crack/ooze on the Beast's muffler (Centek variety) and rescue tape solved that. Rescue Tape is one-part miracle.

Oh, and do not under any circumstances "save money" and buy an off brand. It's about half the price of Rescue Tape, and about half as thick. Plus, the roll I was given is not h1eat resistant to the degree that Rescue Tape is.

I'd given someone the rest of my Rescue Tape who had an issue with his stuffing box. As he was leaving the boat for a bit, the Rescue Tape eliminated the leak until he could get back and re-pack the gland. He didn't have any of that stuff either.

It was a new-to-him boat. And the "rescue tape" he bought sucked bilge water. It didn't appear to adhere as well as the real stuff either.

Since then I've bought another roll. It's about $10 on Amazon. Get clear so you can see through it.
Thanks! Buyen some ta day!

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