The stainless steel exhaust flapper on our Manatee needs replacing but I would like to use a black rubber type replacement. Has anyone found a supply source for the 3 7/16" O.D. exhaust tip mounted on the transom. I would like to fit the rubber type flapper that uses a hose clamp to secure it to the tip but have had no luck. Most suppliers list 3",4",5" etc. the 3 7/16" is probable a metric size but I would think a 3 1/2" rubber type flapper would work if one is made by anyone.