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Old 19-04-2021, 08:04   #1
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Replacing exhaust flapper assembly-which sealent?

I have a 1989 Catalina 30. The original plastic exhaust flapper, (keeps a following sea from traveling up the exhaust pipe), has failed. I have a new all metal exhaust flap assembly that Iím ready to install. So for practical purposes I need to R&R a short piece of pipe that goes through a hole in the transom. Main question is: what sealer should I use around the pipe to form a water-tight seal? I imagine it would come from 3M. Also Iíve been dreading the thought of frozen screws, recalcitrant 30 year old caulk and hanging off the outside of the transom while dropping my screwdriver in the water. Has anyone with prior experience able to proffer sage advice? Thanks in advance!
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Old 19-04-2021, 08:34   #2
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Re: Replacing exhaust flapper assembly-which sealent?

My friend who does this sort of thing for a living recommends Life Caulk, available at West Marine.
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Old 20-04-2021, 04:57   #3
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Re: Replacing exhaust flapper assembly-which sealent?

I'm going to favor a more permanent installation than any caulk suggests. Consider roughing the outside of the pipe and the edges of the hole, and then fairing the pipe into the hull with epoxy, with a small radius on both the outside and the inside of the hull. Leave enough clear pipe outside to get a good grip with the new flapper.

My thinking on it is that this is a waterline hole, and that it is possible, though unlikely, to hit the flapper/pipe on a dock. You don't want to be able to knock it loose.
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Old 20-04-2021, 06:40   #4
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Re: Replacing exhaust flapper assembly-which sealent?

tkeithlu, thank you for the response. Actually, what you describe is what I feared I would meet while trying to remove the original assembly. Fortunately that was not the case and removing the old assembly was easy-peasy. Itís fairly well protected by the stubby little swim step and itís above the waterline as well, so any caulking failure would remain isolated to the stern lazarette.

So all done, none of my worries came to pass. Thanks all.
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Old 20-04-2021, 09:42   #5
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Re: Replacing exhaust flapper assembly-which sealent?

Quote:
Originally Posted by iyamwhatiyam View Post
tkeithlu, thank you for the response. Actually, what you describe is what I feared I would meet while trying to remove the original assembly. Fortunately that was not the case and removing the old assembly was easy-peasy. Itís fairly well protected by the stubby little swim step and itís above the waterline as well, so any caulking failure would remain isolated to the stern lazarette.

So all done, none of my worries came to pass. Thanks all.
I have a Cat 30. The exhaust goes through the hull below the lazarette into an area which connects to the boat's main bilge. At the dock it is above the waterline, but if you are out sailing "on a run", it may not be.

The flapper is there to help prevent water from entering the exhaust in a " following sea', and making it's way back through the exhaust hose , where it could flood the engine and cause dreaded "hydro-lock".

cheers
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Old 20-04-2021, 09:55   #6
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Re: Replacing exhaust flapper assembly-which sealent?

Life Caulk is fine. 3M 5200 is fine.

You really should make sure you have a loop up and down in the exhaust hose to prevent water in the engine.
You may find that heating the old fitting with a propane torch to release the old caulk helps to get it off if it's difficult, but it will likely come off readily. Getting the hose off inside is another story.
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Old 20-04-2021, 11:04   #7
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Re: Replacing exhaust flapper assembly-which sealent?

I should have done this earlier, my apologies, here is a picture of the assembly in question. It attaches to the exhaust hose which snakes its way forward to the aqua-lift muffler. That hose was also recently replaced, (as in the past couple of years). As you can see, it is a simple R&R. My concerns were mostly about getting the old EA out! How I suffered imagining stripping screws and dropping tools in the drink! In the end it was fully cooperative and was a reminder that most of the things we fear never come to pass. Except when they do...


Thanks all for your help! This was keeping me dock-bound.
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Old 25-04-2021, 20:18   #8
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Re: Replacing exhaust flapper assembly-which sealent?

So? What did you end up using as a sealant? I was thinking 3M 4200, but read about using auto permatex too for high heat... not sure it would hold up to salt water.

Thanks,
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Old 26-04-2021, 10:40   #9
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Re: Replacing exhaust flapper assembly-which sealent?

Snoopy, we used Life Caulk which we picked up at West Marine. The assembly was easily removed, especially since I had a young friend of mine balance himself on the swim ladder, one hand for the boat and one for the drill he used to unscrew the assembly. If anyone needs assistance with electrical help or any other boat work just PM me and I can get you in touch. For me heís been a real life saver. Next time Iím out Iíll take a picture of the finished assembly.
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Old 26-04-2021, 18:33   #10
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Re: Replacing exhaust flapper assembly-which sealent?

Thank you.

I was thinking 4200, but I see that Catalina Direct sells the flap with a product called 4000, which makes me think that it’s just 3M 4000 repackaged. I bought the flap a few months ago and want to replace it before it goes back in the water.
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