We have noticed that the boat is running rough the last couple times out. Real rich smelling at idle and white smoke out of exhaust. At high speeds boat seems fine. I have done normal tune up.(replaced plugs and rotor and cap and last year the wires. replaced fuel filter and cleaned the air cleaner. was wondering if anyone had any info on possible problem. Boat has a 351 w 5.8 L ford. with 375 hours. I am second owner and this is my 2nd Nautique first with problems. Last boat was same engine in a ski had 1100 hours. Any help or info would be great. Thanks