Since the OP asked about motors less then 5hp, I will recommend a less then 5hp motor...
Small motors are best sourced in 2 stroke, the weight and simplicity outweigh the slight increase in efficiency... (a small outboard
does not burn that much fuel).
It is difficult to buy a new 2 stroke in the US, but there are many good used values. The Honda
4stroke 2hp is widely considered to be junk by those who have suffered with one (do a search on this forum).
I have owned a few. The hands down best weight/thrust value is the 'canoe motors' made by Johnson/evenrude. They are 2hp, but lack the reverse gear
you are looking for. I had 2 of them, and could easily pluck them off of the rail with 1 hand.
I have a Yamaha 3hp, great little motor but it also lacks the reverse... great motor otherwise.
The best small 2 stroke (IMHO) is the 2 cyl Johnsons that were made up till 99 or 2000. I have a 3.5hp that has 2 cyl and runs very smooth. Mine does not have the reverse gear
, but I know the 4hp did (which looks to be the same motor).
If you can find one, they are smooth and run forever. Yes, the alcohol fuels are a problem, but they mess up any small motor... mix your fuel
in small quantities and avoid alcohol whenever you can.