This engine is a 1978 Evinrude 35HP. The problem is, that it pops out of gear at high speeds. I have adjusted everything I can to no avail. At low speeds it is fine.
Phinfan,Most likely the clutch dog in your lower unit is worn. You will need to disassemble the lower unit to repalce it.If you're not familiar with outboards, I would invest in a $25.00 manual first. The OEM manuals are the best.Check e-bay for manuals, sometimes you hit pay dirt.