Same Problem
John,I thought I'd mention that my 310 also has a sooty transom. It’s usually not too bad unless I really start pushing hull speed (more than 6.4 knots) top speed is 7.1 knots.I'm curious what prop you have, and what cruise speed and rpm you use.I initially thought it was my setup causing the problem. An AutoProp, Universal M25XPB, and 6.4 knots at 1800 rpm (ballpark calibration on the tach which reads 1000 idle and 2700 rpm full throttle in gear, 3000 rpm in neutral). This is my second Autoprop. We went down slightly to 15.5-inch diameter to give 200 more rpm's at full throttle. The Autoprop people swear it's not too large, and the rpm's are characteristic of the self pitching blades.In a way I am relieved that the soot is not unique to my boat. I'd appreciate your comments.BTW, The sooty condition may be more noticable on C310's than some other boats due to the pristine white hull, and the design of the transom.