Internal Exhaust Flapper Diameter?
 

What is the diameter of the Internal flappers used on the 272, 292, 311 SR-1 models of 1988 thru 1990?

Re: Internal Exhaust Flapper Diameter?
 

4" diameter exhaust. Flappers are the "butterfly" type. Vertical hinge bar with two half-moon flappers. They are metal with rubber edges. Rubber burns out first then they make a rattling noise. Eventually, the whole thing, hinge bar and all goes south.

With the Silent Thunder platform in place, you can get by without the flappers. Very unlikely that water will back up through the platform enough to enter the exhaust. Exhaust tips are very high on the transom.

Re: Internal Exhaust Flapper Diameter?
 

Flappers are 3 1/2" diameter.