I have the original gas tank for the same engine and it says 5 ounces per 5 gallons..
it is prefferable to use 10/30 oil mixture because it doesn't harm the motor and the mixture's density is proper
A 35hp Mercury outboard, serial number A184641, 1985 year model.
A 35 hp Mercury 2 stroke, requires a 50:1 ratio, one pint of 2 cycle oil to six gallons of fuel.
my 1979 35hp Johnson is 50/1
A 35hp Mercury outboard, serial number 6445947, would be a 1984 model.
The 35 hp Mercury outboard has a dry weight of 148-150 lbs., depending on year model.
A 35 hp Mercury outboard, serial number A152966, would be a 1985 year model.
The FD 16 A is a 1962 model 18 Hp motor.
The water pump is inbetween the lower unit and the motor . Remove the lower unit with 6 bolts and u will see it.
1959 thru 1963 Johnson and Evinrude use a 24 to 1 ratio. 1964 and up is 50 to 1
http://www.brunswickmarineemea.com/download Click on "Operation and Maintenance Manual", then just drill down to your year and model.
The 1983 model, 35 hp Johnson outboard requires a 50:1 ratio, one pint of 2 cycle oil, to six gallons of fuel.