I am not a fan of additives except seafoam but I have a small issue that I would like some help with. I have a carver 3607 aft cabin with crusader 350 engines. Approx a week ago the port engine started blowing a small amount of smoke thru the exhaust, not enough to leave a sheen on the water (rings no doubt). I P.M. the motor sat and the plugs were clean so it is a new and small bypass. If this were my truck I could snatch the motor, do rings and bearings and reinstall in a long weekend, but this is not only a boat it is an aft cabin, the engine well is in the middle of the salon. To compound the issue I have family that want to spend a three day 4Th of july weekend out. We are crusers 1100/1200 rpms 6/7 knots so I can watch the oil and I will be ok but I hate the thought of the pollution issue. Has anyone had any success with any oil additive. The boat is an 84 so the engines are ready for a rebuild. Have a great day Ed