Loud exhaust on 150

Greetings folks,<br /> This is my first posting, and I hope someone can share some advice. I recently got an '82 Johnson 150 on a 16' Wellcraft. The motor was supposedly rebuilt, and after a break-in period I was able to get to WOT. It starts and runs fine, but after about 15-30 minutes, when back at the dock it seems to be twice as loud as when first started, and the lower unit appears to be shaking/vibrating when trolling along at slow speed. My manual shows a few exhaust seals in the lower unit, and I'm wondering if a bad seal can cause excess exhaust to exit the top rear of the motor (above the water line) and hardly any through the lower prop area. After running it in my driveway during check-out, there was 2-stroke oil leaking from the lower unit/gearcase mating surface. Also, would excess heat cause problems in the vertical shaft of the lower unit?? I called the shop where I bought it and he didn't think there could be any exhaust problem, although I'm bringing the boat to him Monday to check it out. I'd like to be armed with knowledge when I get up there.....He said they did the water pump during the rebuild, too, so I'm wondering if the exhaust seal was disturbed at that time...<br /> Any thoughts?<br />Thanks,<br />Kevin on Cape Cod.......waiting for the rain to stop.....someday...

Re: Loud exhaust on 150

After running it in my driveway during check-out, there was 2-stroke oil leaking from the lower unit/gearcase mating surface

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normal. its unburned 2 stroke mix of fuel and oil.<br /><br />the shaking is probably just the nature of a large 2 stroke at low rpms. mine do it too.<br /><br />couldnt tell ya about the loudness though.

Re: Loud exhaust on 150

Theres an exhaust tube extension that fits on the bottom of the tuner in the mid section. It has a rubber grommet on each end (top and bottom). The grommet or gasket usually holds it in place. Many times they come out when the lower unit is off and they can be a royal pain to get back in. I bet it's missing from yours.

Re: Loud exhaust on 150

Thanks, myoutboards, but it wasn't the oil itself I was wondering about, but the area it was leaking from. Coming from the lower gear case/lower unit seam. (some was coming from the prop area, as I would expect, too). I think DHadley may have shed some light on this, and I'll be mentioning the tube extension when at the shop on Monday. If this were missing, would performance be affected as well? I assume so due to the exhaust tuning not being up to factory specs.<br /> Thanks again for the help,<br />Kevin

Re: Loud exhaust on 150

At the rpm I suspect you're running at the performance will not be affected. But, as you suspect, with that extension missing or not sealed properly the gas/oil will leak out that seam.