I went ahead and put the clamp on flappers on the tips where they come through the transom. I figured it couldn't hurt.

Hope the clamp on flappers make it thru the holes in ST.
I was going to do the same thing when I had my 272. But they wouldn't clear the deck

so reviving this thread from the dead a little. just curious I noticed this weekend that I have this similar gasket leak between the platform and transom. it seems pretty small as I don't really notice the exhaust leak too badly or at least not enough to bother me. Does the gasket also seal up between the actual exhaust and the transom or just between the transom and platform? i.e. am I exposing my transom core to water with the gasket leak or is it just more a nuisance that isn't really doing some kind of damage. Thanks!

My 89-272 SR-1 Transom was sealed with brass tips. The ring gaskets only keep the exhaust gasses from coming out around the gap between the Silent Thunder and transom.
The seals also prevent blistering the gel coat from the heat of exhaust.