Looking for some inspiration in determining the position of the exhaust/muffler setup for 22 ft boat
the BBC + turbo (under hatch) is fitted off the transom with inline Z-drive, crash gearbox behind motor
the rear deck/cap slopes down to transom and as my hatch is off the transom approx. 24", was thinking would run the pipes up from inside engine bay through rear deck and then elbow back to follow deck profile and then hang some gibson mufflers i have here

Understand this is a little different setup, however looking for any photos of exhaust pipes coming up through rear deck as opposed coming out of transom
anyone got anything to share
I'll post photo of the rear deck deck setup in few hours after i clear the crap of the boat

first some photos of the boat and transom and rear deck

Mocked up 4" tail pipes with mufflers, these are 6" off centre
was thinking that if i drilled transom for pipes they may be sitting a little low, as gunwale not that high like offshore boat

its large hole to cut so only want to do it once

well after deep contemplation while knocking back a few beers on saturday thinking what and how to do this routing of the exhaust pipes, decided to get up early on sunday and cut a few holes in the rear deck and will bring the pipes out there as opposed to through the transom

had some 4" x 15" 316 stainless 0.80" here and used a 90 degree storm water fitting to mock up proposed exhaust tails and to support muffler

exhaust mock up

originally i was thinking the exhaust tails/pipes after they come through the deck of boat could be dry no cooling water

But then thought may need to double skin the exhaust to get some cooling as pipe goes through deck
Therefore not sure whether its possible to put a cooling ring between the 4" exhaust pipe and the deck
could make this 150mm dia x 30-50mm deep (deck at rear is 20mm thick), this would have water continuously flowing through to cool the pipe around the deck

any thoughts on whether this would work ??
excuse my rough sketch

Probably aware, but just in case, sharp 90* angles is no bueno.

yes, would be 90 degree radius elbow, I think the length is of bend is 200mm (8")
its probably just the way i have sketched it

What kind of mufflers are those?

Ayuh,..... In my experiences, ya need jacketed pipes all the way, til the rest of the system is droppin' downward,......

Otherwise, you'll be pourin' water into the motor via the exhaust,.....