Why do my rubber exhaust flappers keep failing?
 

When I got the boat last spring it needed two new exhaust flappers so I replaced them (internal rubber flappers).

I just noticed that they are both bad again after 30 hours. Any suggestions? (IMCO Power Flow exhaust straight out the back bolted on a stock 502)

Mike
Portland Oregon

I can think of heat degradation and abrasive degradation as two possible causes.

Heat - is there any discoloring of your risers? I'm not familiar with the imco power flow - is it stainless? How's the water flow, and restrictions in your system?

Abrasive - is there sand or other particles in your water? How's the condition of the impeller for the raw water pump?

What kind of rubber flappers are you using? Maybe there was a bas manufacturing batch?

Ryan

Most common failure is due to lack of water in the exhaust stream. It is used to cool and lubricate the flappers.

When I got my boat all of the flappers were were missing (twins) also three of the four in my "Y" pipes for the Silent Choice were the old style and missing as well. I replaced them all then had an impeller issue on one engine and guess what the exhaust flappers were gone again... If the boat is new to you I would flush the block, all the lines, back flush (or take apart) the cooler and change the impeller as well. You never know what is lurking in the system from the previous owner and you would be surprised what you find. As stated above it sounds like you might have a flow issue so check everything!

not enough water flow causing them to get too hot

It can be your exhaust set up restricting some of that water flow

I use corsa tips with metal weighted internal flappers (The have rubber on the edges of the blade). They might be noisy, but they don't break.

I absolutely hate those. Always sounds like a low volume bottom end knock when idling. Drove me nuts.
OP, I agree sounds like lack of water.

mark..i have metal ones also..bur are rubber coated and make no noise..

Mine had rubber around the edges. Took a sawzaw to them and put the rubber caps on.

I've burned 2 sets last season within 1 week of run time and the manufacturer replaced them under warranty, but after the 2nd time lasting less than an hour, I took them out and don't have anything at this point. Going to reinstall this season again to see what happens. I have SM full system.