7.4 liter rich exhaust smell
 

I have a 1994 searay sundancer 290 with a 7.4 liter mercruiser (weber carb) and bravo 3. Over the last year I have had a problem with the exhaust smelling rich. I have also noticed minor amounts of black soot on the exterior of the transom and a slight oily/gassy sheen visible on the surface of the water when the motor is running. The performance of the motor is fine except for the odor of the exhaust. The last time I took the boat out there was smoke present upon start-up, not normal, which was accompanied by an extraordinarily strong rich smell. The smoke stopped after about 3 minutes of running and the odor significantly reduced although was still present. Any ideas where to start to remedy the problem. I did check the choke and it is in the full open position upon engine reaching normal operating temp.

Thanks.

How many hrs on engine, what color is the smoke color can tell you what extra you are burning

engine has 580 hrs on it. the smoke was grey but only smoked the last time i started the boat. never smoked upon start up before.

Prob just burning a little oil, black on transome is from fuel with ethanol in it, running rich could be carb out of tune a little, when was the last time you changed spark plugs

just changed plugs and wires last month. there were two plugs that were black and dry all others were slightly brown.