builders, "for the finest marine silencer both in safety and noise control". It's a fascinating history lesson researching old boat parts. In fact, I found one for sale on Ebay for 90 bucks(!?)
I removed the cast iron muffler. It's surprisingly heavy for it's size (Maxims smallest - for sailboats), and has chambers of some sort. The muffler is located aft and downstream of a the high bend below the aft deck.
A tap and pipe receives the raw water from the jacketed pipe and injects it into the muffling chamber. Then cooled and muffled, it runs to a larger dia. rubber hose, and out the stern. The biggest difference in the sound is at idle, there's no surging gurgle, just a constant soft muffle. At speed it sounds (to my ears) the same as more typical (today) marine exhausts as both have a constant stream of water mixed in the exhaust.
The Maxim Silencer company survives (over 100 years I think) and looks like a large fabricator of industrial silencers. They still make some marine mufflers for larger boats I think. A success story of high quality manufacturing.