oil additives

[e burger]

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

[AaHubb]

If the smoke is from oil and not steam you could just have some gummed up rings. One trick I used 'long ago' was to do an oil change but the last quart was either solvent or tranny fluid. I would run the engine for a 100 miles or so then change oil again using a good detergent oil. Really helped reduce the blue smog some of my old cars left behind.
..Aaron

[waybomb]

I've done that too AaHubb.
On a boat though, I wouldn't run it long and run at low rpms.

On a non-boat subject, a friend's mother had an 80s Impala, mint, hardly any miles, like maybe 20k, never changed the oil drove a max of a couple miles at a time. The engine was clanking and knocking and not sounding good at all. He asked me to take a look at it. The oil was like crude - thicker than any gear oil I've ever seen. Opened up the drain plug and had to help the sludge out with a screwdriver.
Filled that puppy up with diesel fuel, started her up for a few minutes. Drained it, and did that maybe 5 or 6 times. Changed the filter and 5 quarts of 10 40, ran it for a day around town, changed it all again, gave it back to her, and a good scolding to her, told her change oil every 3 months no matter how many miles she drove. I lost touch with them many moons ago, but that Impala ran for at least another 10 years.