Fuel/oil mix for older motor

I just had my 1967 6 hp Johnson tuned up - new coils, wires, plugs, lower unit oil changed (including new seals), and the thing runs like a top. My mechanic did, however, recommend adding a little extra TC-W3 to the mix, since it is an older motor and would benefit from the extra lube. Do you all concur, and if so, what ratio would you recommend. If my math is correct, I have, in the past, added 1 pint of TC-W3 to a six gallon tank, which should result in a 1:48 mixture (essentially the 1:50 mix usually recommended here). I wonder if I added the same pint to 5 gallons of gas (yielding a 1:40 mixture), if that would be good?

Also, being new to this game, I wonder how long I should expect this little motor to push my light-weight 14' jon boat with a three gallon tank, with just myself and my fishing stuff. Any ideas?

Re: Fuel/oil mix for older motor

Never mind the "how long will it run question" - I searched around and discovered a rule of thumb here that suggested 1/10th gallon per hour per horsepower which would give me roughly 5 hours of running time for a 3 gallon tank. Tht's a lot of running!

Re: Fuel/oil mix for older motor

I would agree with your mechanic. 40:1 would be a better for that motor.