351 carb tuning

just wondering about carb adjustments for my nautique with a 351. it has a holley 670 with, what i am assuming, are stock jets. after about a day of riding, the back of the boat is covered in black exhaust deposits. and if i remember correctly on initial start-up and idling it seams so smoke somewhat. would this be carb related? i was told it could be burnt oil but just didnt sound right. i was thinking it was the carb becuase with WOT i stick around 38-40mph with a 13X13 prop. if so, should i reject or try to tweak what i have.

Chad , we dont care how you spell it is how well you listen.......
If it is indeed the stock Holley it is a model 4160 with a cfm of 600.
And yes the black soot on your transom could be related to the low speed or idle cicuit being to rich.
A vacuum gauge gives the best results , highest reading in gear that will allow for instant starts without adding Any throttle will give you a cleaner transom.
This is not hard to do but requires a little patience, 3/4 round out will give you a good starting point.........Boat dr

i knew it need a little attention as far as tune up is concerned since the person i bought it from a year or two ago ran it very seldom. they replaced the stock carb with what is on there now, which i looked up and found it was a 670 CFM. since they carb was diff i figured thats where i should start. i havent changed cap, rotor, wires, or checked initial timing. all i did was change plugs, oil and set idle because i was ready to ride when i got it and never have gotten around to anything else. and yes the smoke has a blue color to it. so im assuming start with the ignition overhaul and then the carb since im not really carb tuning inclined. thanks for the input