I pulled my exhaust elbows today on my new-used boat to verify if the flappers were still there, and found one missing and one at the bottom of the Y pipe. I have a set of aftermarket exhaust risers, and the flapper pivot holes are round with no provisions for the square locking pieces like on the stock setup. The flapper I did find had a completely round shaft as well. There are no markings on the exhaust castings that I can find, so I'm not sure what brand they are.
