"My 2010 6 HP Mercury developed an exhaust leak near the backing plate of the swivel mount. I took it to a local shop, which informed me that I will need two new bushings and the backing plate itself (because one of the bushings vulcanized and adhere to the plate so that they cannot clean it properly) to a tune of $300. After I looked at the diagram of the engine, I asked what might have caused it. They said "engine overheating." So I said "that engine never overheated, but you guys were supposed to find an exhaust leak near that location." They said "oh, sure exhaust leak might have something to do with it." so I said "OK, so replacing bushing and back plate doesn't really fix the problem, does it?" They reluctantly allowed that it does not. Setting aside the issue that I was about to spend $300 without actually fixing the problem itself, I asked where that exhaust leak could have happened, and was it a gasket (they recently replaced the impeller in that engine) or a part failure. They didn't know, but a "Mercury guy" was supposed to have a look at it this week. As I am not hopeful, I wonder if anybody here could help. Specifically, how is exhaust routed in that engine? And what is the most likely cause of the leak itself? I do not think the bushings were meant to seal off the exhaust. I found a diagram of the swivel mount (so I could understand what they were talking about) but there is no diagram of the exhaust system. So, any help/advice would be appreciated at this point."
2/14/16
I had a look at the engine. The exhaust leak is from the opening where the shifter link exits/enters the engine housing on the way to/from the shifter handle (below the swivel). The bushing that melted is the upper one used with a friction clamp to clamp it to the internal "pipe" (housing driveshafts and the exhaust) to control the engine swivel. I concluded that the melting was facilitated by the internal conduit overheating. The exhaust leak is due to the exhaust gasses buildup inside the engine. That build up is likely causing the internal conduit to overheat. As there is no "exhaust pipe" in there, the only possible reason for both of these things happening is some kind of blockage of the exhaust gasses outfall (they are routed via prop shaft). The only thing that happened to that engine was the water pump impeller replacement last winter. So, in my mind, the lower unit needs to come off so we can inspect/ clear the exhaust passage. Feel free to disagree...
2/25/2016
Solution found! The overheating of the rubber bushing was due to me overtightening of the friction screw limiting the swivel of the engine. Too much pressure (screw too tight) caused the bushing to be tightly bound to the exhaust conduit, which caused melting.
The exhaust leak was due to the fact that the small rubber grommet around the opening in the engine where the gear shift comes out to connect to the shifter handle was left out. This allowed a small amoint of exhaust gasses to escape. Parts are on order (bushing, 2 thrust plates, and the grommet) and the engine should be ready in a week!
2/14/16
I had a look at the engine. The exhaust leak is from the opening where the shifter link exits/enters the engine housing on the way to/from the shifter handle (below the swivel). The bushing that melted is the upper one used with a friction clamp to clamp it to the internal "pipe" (housing driveshafts and the exhaust) to control the engine swivel. I concluded that the melting was facilitated by the internal conduit overheating. The exhaust leak is due to the exhaust gasses buildup inside the engine. That build up is likely causing the internal conduit to overheat. As there is no "exhaust pipe" in there, the only possible reason for both of these things happening is some kind of blockage of the exhaust gasses outfall (they are routed via prop shaft). The only thing that happened to that engine was the water pump impeller replacement last winter. So, in my mind, the lower unit needs to come off so we can inspect/ clear the exhaust passage. Feel free to disagree...
2/25/2016
Solution found! The overheating of the rubber bushing was due to me overtightening of the friction screw limiting the swivel of the engine. Too much pressure (screw too tight) caused the bushing to be tightly bound to the exhaust conduit, which caused melting.
The exhaust leak was due to the fact that the small rubber grommet around the opening in the engine where the gear shift comes out to connect to the shifter handle was left out. This allowed a small amoint of exhaust gasses to escape. Parts are on order (bushing, 2 thrust plates, and the grommet) and the engine should be ready in a week!
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