Mr Jones is right. I may not have said it in quite the same way, but a boat buck can certainly point you in the right direction to self reliance.
Sounds like it may have had a stuck/sticky valve. A nice oil change with some form of additive may have corrected the problem. Or it may not have. The point being that there is no real mystery to be found under the cowl of an outboard, and doing it yourself (in this particular case) wouldn't have left you any further behind than just leaving him with your motor.
Pay your tithe, get your motor back, and play around with it.