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Exhaust and Noise Issues with Transom Well Mounted Outboards - a Fix  

August 6, 2017. John Wadman lost his Yankee #141, Barbara Joyce, in an arson fire in Columbia. He offers the follwing comments re engine compartment issues with transom well imboards. Click here to go to Barbara Joyce's page

I was reading some posts on the Forum about the poor engine compartment in the Dolphin and offer some observations about that.

What I noticed about using my Suzuki 8 hp two stroke motor to propel Barbara Joyce was this. . . First, if I closed the compartment lid, the exhaust would fill the compartment and eventually choke the motor out. So I had to motor with the lid held open with a hook the clipped to the back stay. The hook is nice to have so as to be able to service outboard and work in the locker. BUT, with the lid open the exhaust comes into the cockpit choking out the crew instead of the motor. Plus, the noise is horrendous!

A friend solved this problem by putting two tall dorades in place of those lower profile clamshell type dorades vents. One he pointed forward and attached a duct hose to it under the deck. Then he cut a hole in his OB engine cover with a hole saw and made a PVC fitting sleeve out of a PVC nut and another threaded to regular slip/glue fitting that he screwed into the hole. To this he slipped the  duct hose over it. It seemed to solve the problem but I was worried that if a wave came aboard and washed down that side deck and went in the dorade vent that it might send water into the engine cover. And obviously, if the weather is bad enough to do that, that would be the absolute worst time to have the engine get flooded with salt water!

I analyzed the problems. First the exhaust gasses and second the noise. I realized that if the gases didn't come up in the well then the lid could be left down. If he lid could be left down, much less noise. So I got some wax paper, tape, surfboard glass cloth, epoxy resin and a piece of 1 1/2" PVC pipe. I taped the wax paper over the exhaust holes on the back of the OBs lower end, mixed some resin and cut some pieces of cloth about 4x4 inches. I laid up about 5 layers and let it kick off. This was the flange.

While I was waiting I wrapped wax paper around the section of 1 1/2" PVC pipe and taped the ends tight. You want to wrap it several times around to make the fiberglass piece easier to remove when it's cured. I then took 2" fiberglass tape and wet it out and started wrapping it around the pipe until it was about an 1/8" thick and left it to dry also. With those hardened, I removed both pieces of fiberglass and trimmed them and removed the wax paper and tape from the OB lower end. I then drilled a hole in the center of the first piece with a hole saw that matched the O D of the fiberglass tube I had made. I then used some 5 minute epoxy paste to glue the tube to the flange.

Once this cured I tore little pieces of fiberglass strand and started glueing them around the joint between the tube and the flange. I glued the tube at about a 30 degree downward angle on the flange, this is very important. Once cured I sanded it, trimmed the end of the tube at an angle and cleaned it up a bit, then I drilled 4 number eight holes in the flange, one in each corner. I now had a fiberglass exhaust manifold.

I placed the manifold on my OB over the exhaust holes and marked with a marker each of the 4 number eight holes with a fine tip marker. I used a metal punch to make a depression in the first hole and then drilled and tapped it for the number eight screw. I lightly tightened the first screw to hold the manifold secure as I drilled and tapped the other three holes. I then removed the exhaust manifold, applied a little caulking and reattached the SS screw with thread lock. DONE! The tube angled down just under the waterlevel and the exhaust came out underwater.

By the time it surfaced the boat has moved forward enough so that it comes out behind the boat. The well lid can be left down and everything is much quieter. Just the fact that the exhaust comes out underwater cuts the noise down immensely! In rough seas the stern will lift occasionally and you will hear the roar of the exhaust momentarily but it doesn't affect the air to fuel mix in the engine compartment as it still comes out behind the boat.









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