What Year 40 Johnson?

[outbdnut2]

I bought a 40 Johnson yesterday and the model and serial numbers are rubbed off – looks like from a steering cable crossing over on a rig where both cables went down the same side of the boat. The welch plug is missing…..or, who knows, maybe it was stolen at some time in it’s life? So I’m trying to determine the year. Not sure if the case has been swapped. The case has had some touch-up paint many years ago, as it has turned chalky.

It’s definitely a 1960s era 40 HP. It is new enough to not have the electric cable socket on the side, and the carb high speed jet is fixed. The automatic choke is the old hot-water type, and the front of the carb has a white plastic piece behind the low speed carb jet knob. I’m thinking 1961 or 62. If the cover is original, the label inside the access door gives instructions for 24 to 1 oil/gas mix. I appreciate your thoughts on what year it could be, and any other things to look for that could identify the year.

Photo below.
Thx, Dave

[frankr]

Crankshaft was changed 1962. Easy way to tell is check the size of flywheel nut. Without going out to look, I think the 1961 was 1-1/16″ hex, 1962 was 1-5/16″ hex. Kick me if that is not correct.

EDIT: Hold off on the kicks. On second thought, I think the small nut is 7/8″ hex and the larger one is 1-1/16″ hex. Still subject to verification, ’cause I don’t have one.

• This reply was modified 2 years, 12 months ago by frankr.

[outbdnut2]

The flywheel nut is the bigger 1-1/16″ hex, so it must be 1962 or later. The automatic choke mechanism changed in 1964, so it must be a 1962 or 1963.

Did that crankshaft change come with the change to 50 to 1 gas/oil mix?
Dave

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