Engine exhaust transom through hull fitting

Hello All,

I need to replace my chincy crumbling plastic exhaust fitting and have a few questions:

  1. what size exhaust hose and fitting do you have? i figure this is typically sized to the engine… I’m pretty sure I have 1.5" on my 10 HP Sabb. I’d be interested in both other Sabb owners and what modern 25-30 HP volvo/yanmar/etc owners have.

  2. do you have a shutoff valve? I think some boats have this installed to prevent severe following seas from back filling the engine. I can’t say I’ve ever had that problem and I’m not sure how much utility this is given the conditions most of us sail our boats in.

  3. does anyone have a bead on where I can buy a good fitting? SLM used to have the fittings custom fabricated. bronze preferred… threaded preferred - so that I can attach a threaded elbow and go up… Maybe I’ll check with Cape George - has anyone worked with them on parts?


In replacing our exhaust system we have some parts. The bronze exhaust fitting that came out is for 1 3/4" hose. Looks to be in good shape and is threaded so it could be reduced down to the size that is needed.

Bob & Lois

BCC Jolie Brise

Jeremy ,BCC Calliste 072 came with the standard SL Morse bronze exhaust fitting,
but I had to raise it on the transom, 6" ,
because I load my boat heavy, and the stern wave was partially covering the exhaust when motoring,
and that sputtered carbon drops all around on the transom.

Sorry that I don’t offhand know the size of that hose.

I too installed a ball valve and elbows on the inside of the transom, just above the exhaust outlet fitting, but have never used it. I did think that if I closed that valve, and forgot to open it, that it might blow off the exhaust hose when starting the engine,or the back pressure might prevent the engine from starting at all.

When I replaced the original Volvo 2002 engine with a 3GM30 Yanmar, I used the same water lift (Vetus ?) silencer, but did make the manomometer test, that Nigel Calder reccomends.

Also, I did install one of those black rubber exhaust flapper valves, on the outside, too.

Because the Yanmar uses such soft shore motor mounts, I wanted to use a bellows type hose between the engine exhaust elbow and the water lift silencer, because when I connect the exhaust elbow with a stiff rubber exhaust hose to the silencer, it throws my prop shaft coupling out of alignment, but I never could find a small enough diameter exhaust hose bellows or even a “hump” hose, that would fit, so have to rely on the flexable shaft coupling to compensate for the shaft missalignment.


Todd Uecker of CGC is excellent to work with. Very helpful. His direct EMail address is cgmw@olympus.net. He is not always there and may be a while before he returns your EMail. You can call him as well at 360.385.3412

He can get you anything you need but because they are new with the parts it does sometimes take him a little time to figure out exactly what you want an where he put it.

Any of those fittings can also be bought from Port Townsend Foundry whom Todd ultimately works with anyway. Some people find Pete from PT Foundry difficult to work with but I think it’s only because he is a very busy guy. I’ve used Todd to get things from PT Foundry from time to time.

Good luck


PS. Douglas, where exactly did you mount your exhaust? How many inches above the waterline or the middle gudgeon? Thanks…

Ahoy Bryon, I just moved the brnz exhaust outlet, that was factory installed, up higher on the transom , by 6" .

I will try to attach a pic for refrence, here with.

I covered the lower abandoned exhaust outlet hole with a Butyl rubber gasket and 1/4" thick round bronze plate.

I might have a clearer pic, but that would take some time to locate.


PS: If you zoom in the pic, you can see the black soot acumulation, on the transom begin above about the middle of the original lower exh outlet, this is where the stern wave water line is. My boat was loaded with provisions and play toys, on an extended expedition to Thailand’s, Pang Nga Bay, these are mostly flat water, lake like, sea conditions , and mostly motoring, little wind .

Ok folks - I’ve locked in my plan. I’m going to put in a 2" exhaust through hull; mated to a 2" vetus gooseneck; and then reducing down to 1.5" to mate the existing 1.5" hose from the engine. I’m hoping this might tame the Sabb exhaust a bit, and leave me prepared for a future repower.

Now for the joys of enlarging a 1.5" hole to 2"…


Enlarging a hole - three techniques

  1. Plug the 1.5" hole with either a wood plug or fill the hole with a thickened vinyl ester resin. Epoxy could be used but it takes longer to cure. In a piece of thin cardboard, cutout a 1.5" square. Place the cutout over the 1.5" plugged hole in the hull and mark the corners. Connect the corner marks to find the center of the 1.5" hole. Using a 2" hole saw, cut a new hole.

  2. With a hole saw cut a 2" hole in a piece of plywood. Using double sided carpet tape, stick the plywood template over the 1/5" hole. With your freehand, hold pressure on the template, and cut the 2" hole with a hole saw.

  3. With a hole saw cut a 1 3/4" hole out of 1/2" or 3/4" scrap plywood. Mount the center of the “hole” (plug) on a 1 1/2" long 1/4" diameter bolt or machine screw. Chuck the bolt/machine screw into a drill. Turn the drill ON and taper the end of the plug with sandpaper until is just starts to fit into the 1 1/2" hole in transom. Remove the bolt/machine screw from the plug and set the plug into the hole with a mallet/hammer. Drill a 2" hole using the 1/4" hole in the plug to guide the hole saw.

I like technique 1 and 3 the best. With technique 2 there is a possibility the template could move.


I vote for 1)! Have used it, and it works great.