Transverse muffler solution
 

In the 80s, my Dad built a set of stainless exhaust manifolds for a 350 powering a Volvo 280 drive.

It was/is in an 18ft K&C boat. Just a regular runabout made in Vancouver BC.

What they did was also fabricate a transverse muffler system, that mounted up close to the transom. All wet flow, that exits to thru-hull with flappers. The intent was to maximize flow, while eliminating a lot of the bark from thru hull exhaust.

It seems this would a good solution to a lot of the bark issues from thru-hull and maintain high flow.

I like a good V8 bark as much as the next guy, but muzzling it to an acceptable level without being abnoxious, would be great.

On my Glen-L Thunderbolt, with Nixon ex manifolds...no risers...I can look into the hull port and see the ports to the head.

I'm looking at making up a transverse muffler system for my Formula 233. With TRS, it has even more room to have a tuned exhaust system.

Likely go with EMI manifolds, and fabricate risers to drop and feed the muffler, to thru-hull.

Was thinking injectjng the raw water in the muffler vs risers...to prevent reversion, and get better cam timing.

Mastercraft boats do something kind of similar. Not a muffler per say but puts it under water to make it quiet. Lol. It’s called ‘Fresh Air Exhaust’ just because puts exhaust inwater vs in air bothering skiers/boarders.
Anyway - i like your thinking. Keep us up to date on your progress.

https://cimg1.ibsrv.net/gimg/www.off...607707b070.jpg

Nice looking setup.

My Thuderbolt exhaust isn't too bad in the boat...but wherever the back end is pointed...is rugged.

A proper manufacturer ski boat would have to have a quiet exhaust to keep the girlfriends and wives happy... !!

One of the factors I have to contend with, is what height to make the thru-hull on the Formula 233. It has the factory swim grid, but I'm not against moving it up a touch.

I wanted to beef up the swim grid slightly to mount a 2-Stroke kicker. Something easily mounted in some water...and not obtrusive. But I hate the idea of a single.
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https://cimg0.ibsrv.net/gimg/www.off...a91b9fb6bf.jpg

Here is the 350 Volvo 280.

Drive has about 20k hours on it. Mostly all original. Well maintained.