mine wont work then as they are for 4.5" pipes.

Assuming this is just for freshwater Ontario?

Seafordguy, They are twins, mine is also blue and honey..originally a 454 with TRS, now 502...

Yes, I'm on Lake Huron, and sometimes run it in Georgian bay...

You can definitely run silent choice on a TRS, look at the inner transom plate and you can see the tri-lobe block off plates on port and starboard.
i know for sure as i had to install silent choice on my Formula F-302....

Do you have any part numbers, or any idea where I can find a drawing? I looked thru merc parts but can't find anything....

Do you have any part numbers, or any idea where I can find a drawing? I looked thru merc parts but can't find anything....

I'm sorry i don't have PN's or a diagram, it was a long time ago for me
a quick "trs silent choice" search online and you'll find the diverters but i cannot locate anything on the left and right adapter pipes you need for the inner transome plate.
perhaps someone with manuals will chim in

You're going to have to fabricate the entire setup.

Pull the aluminum caps off the inner transom plate, have someone fabricate a flange from it with a pipe so you can make a connection between it and the Silent Choice Y-pipe. Seal your new flange/pipe using red high-heat RTV. Shouldn't be difficult to make but not cheap either when you consider sourcing the Silent Choice parts to make it all work.

Easier to just add inserts:

https://teaguecustommarine.com/stain...uffler-inserts

$120 ain't bad at all considering your other options. Also, adding external (salisbury) flaps can take the bark out of it, too. **Here in Virginia they seem accept the flappers.