I have searched high and low (and related threads) and have not been able to identify a muffler/silencer that is 4" diameter and can be slipped into a through-hull exhaust tip. I an running an exhaust for idle/slow speed and need to really reduce the noise levels. Suggestions?? Thank you!

https://www.hardin-marine.com/p-1262...-silencer.aspx

The install video of those silencers was cringeworthy. I wonder if these would fit with the flappers that are going to be in my new tips..

Any specific reason your against a external clampon?

Other than I don't want hardware hanging off the transom. My preference would be inserts. The Hardin units (I am told) only reduce 12dB. I am looking for a rumble similar to a ski boat

want my boat to sound like a ski boat...........

What engine are you running, what HP ?

The best way is going to be diverting a part of the sound through the Y pipe IF you have one. Those slip ins above won't have that great of sound and will really hurt your performance.

Id go with the clampons, the look never really bothered me. Then your internal flappers stay intact. The gibson bullets are really fairly priced and hardly hurt performance

If you have a bravo drive, depending on the engine, I have the aluminum Y pipe I took off my boat for sale. There are also tails for it, but not sure they would fit what you have, and mufflers that bolt to the swim platform. it was really quiet when on the fountain and only could hear the engine when underway. could barley hear any rumble unless you were right behind it.