Sportwins were rated at 9.5 horsepower and ran from I guess the late 60's to 74 when they were rplaced by and updated 9.9. So yours could be any of those years. 9.5 hp @ 4500 rpm WOT range is from 4000 to 5000 RPM it has 15.2 cubes with a bore of 2.3125" and a stroke of 1.8125" it had a 1.76(13:23) gear ratio and scaled in at 60ibs.
