Metal exhaust flappers


2

206LSdrvr

New member
I'm looking to replace the neoprene(?) flappers in the exhaust tubes that pass thru the transom. I want to use metal ones, but the only ones I have seen appear to have the flapper shaft located off center. Does anyone know where I could find any that have a center shaft that would be a direct replacement for the Mercruiser parts. Do I really need them?
 
Car Biz said:
I cut mine out. With the thunder box i dout you will need them. ;D
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That's what I wound up doing. there are 4 screws that hold them into place so it was no big deal to remove them.
 
206LSdrvr said:
I'm looking to replace the neoprene(?) flappers in the exhaust tubes that pass thru the transom. I want to use metal ones, but the only ones I have seen appear to have the flapper shaft located off center. Does anyone know where I could find any that have a center shaft that would be a direct replacement for the Mercruiser parts. Do I really need them?
Click to expand...

My understanding of the shaft location is that it must be off center or the back rush of water would not close the flap.
 
The Mercruiser flappers are a butterfly set up on a center shaft. The are made of a neoprene? material are molded onto it and there is no hinge. They flex back and forth. The after market ones I have seen are 1 piece hinged on an off center shaft and these work like you describe. I had replaced the original flappers about 3 years ago and when I put my new exh. system on I noticed they neede replacing again. If I pull the Thunder box off I may replace them at that time with the metal ones.
 
206LSdrvr said:
The Mercruiser flappers are a butterfly set up on a center shaft. The are made of a neoprene? material are molded onto it and there is no hinge. They flex back and forth. The after market ones I have seen are 1 piece hinged on an off center shaft and these work like you describe. I had replaced the original flappers about 3 years ago and when I put my new exh. system on I noticed they neede replacing again. If I pull the Thunder box off I may replace them at that time with the metal ones.
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If you pull the box off just buy the black flappers on the outside. I will be loud though ;D ;D ;D
 
Sometime in the not to distant future I've got to pull the box to replace the gasket that runs around the perimeter so I can do something then. Since I've got the boat out of the water now it may be the time to do it. If I put the flappers on like you mentioned I don't think it would be any noiser.
 
206LSdrvr said:
Sometime in the not to distant future I've got to pull the box to replace the gasket that runs around the perimeter so I can do something then. Since I've got the boat out of the water now it may be the time to do it. If I put the flappers on like you mentioned I don't think it would be any noiser.
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I have my box off right now and it is LOUD ;D ;D I will be putting it back on next week. i want to run it one time to see if i gain any speed or rpm with it off. ;)
 
With the box off I bet it's loud! I have thought about running exhaust tubing through the box directly to the existing exhaust outlets. I think a couple of guys have done it on OSO. One even had transition pieces made up to adapt to the rectangular outlets. If I did it I would use round exhaust flanges. It would be a lot simpler to plumb.
 
206LSdrvr said:
With the box off I bet it's loud! I have thought about running exhaust tubing through the box directly to the existing exhaust outlets. I think a couple of guys have done it on OSO. One even had transition pieces made up to adapt to the rectangular outlets. If I did it I would use round exhaust flanges. It would be a lot simpler to plumb. 
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That is the reason i took it off was to plumb pipes thru it just like RAMBUNCIOUS on oso did. ;D ;D After looking at the cost factor and time to do it i lost intrest. You are 100% correct about using round flanges. There is a member of speedwake that is doing the round pipe but he is going to use the flex water hose. Good luck. CB
 
Car Biz said:
206LSdrvr said:
With the box off I bet it's loud! I have thought about running exhaust tubing through the box directly to the existing exhaust outlets. I think a couple of guys have done it on OSO. One even had transition pieces made up to adapt to the rectangular outlets. If I did it I would use round exhaust flanges. It would be a lot simpler to plumb. 
Click to expand...

That is the reason i took it off was to plumb pipes thru it just like RAMBUNCIOUS on oso did. ;D ;D   After looking at the cost factor and time to do it i lost intrest.   You are 100% correct about using round flanges.  There is a member of speedwake that is doing the round pipe but he is going to use the flex water hose.  Good luck.  CB
Click to expand...

That's why I thought about using the round flanges. The cost of having stainless square to round transition pieces made up had to be expensive. I was planning on using flex hose too. Some fiberglassing would have to be done on the back of the box to mate with the flanges, but it's got cheaper than fabricating stainless.
 
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