[Fr. Frank]

From Here: http://boatinfo.no/lib/yamaha/manual...maha.html#/616
and from an Australian Yamaha dealer website:

Yamaha 40V HMO
"V" =3-cylinder, 698cc block, 2-stroke
"M"=Manual [pull rope] start w/o charging system (could be easily changed to electric start by adding starter, key-switch, magneto and flywheel. The wiring was already there)
"H"=Tiller handle, with handle-mounted gear shift,
"O"=533mm shaft length, (21 inch shaft)

This basic motor was sold in Asia beginning in 1980, the market expanded to include Australia, Africa, South America and the Caribbean in 1985, and sold in the US from 1997 to 2003, and then the model was discontinued in 2005.
The "Autolube" model came after the earlier "Precision Blend" model, first appearing in 1998.

Narrowing it down any further than that needs the information off the serial# plate on the left side of the transom clamp.