I have the old 1966 interceptor manifolds with straight exhaust through the transom on my Ski Sporter. It sounds so nice with that 289 in there, but I am always worried about water getting sucked back into the engine. When I slow down from planing, I always "bump" the throttle up a bit to stay in front of the water surge behind the boat. When launching or docked, I always wedge some silly toy rubber balls in the openings, but I would like to install some type of real flapper internal to the original exhaust set up.
I have tried to clamp some rubber flappers on the outside and as the motor came up to more than an idle leaving the dock, they both blew off and sank.
Is there a flapper that can be slipped inside or a way to modify my existing setup? I would like to keep the original exhaust trim rings for the right look. And another followup question is will it change the sound of the exhaust much?