The sticker on the side of my 6hp two stroke Suzuki OB reads 100 to 1. Unsure of the year.
If you are using NGK plugs, the plug model is BP6HS and the gap is 0.035. I had to look it up also for my 6HP Suzuki outboard on my sailboat.
.035
50:1
Model number 6303, would be a 1973 year model, 6hp Evinrude outboard.
Johnson 6hp spark plug gap
50.6
My best guess would be about 5-8 mph
it weighs 27kg
The correct plug gap for the 1971 model, 6hp Johnson outboard, is .030-.035 in. It requires a Champion J6J, or NGK B6S.
50:1
RJ8C Champion
The Johnson model CD25R, is a 6hp outboard, produced in 1968.