Folks,
We picked up a solar charger for less then 60 dollars at canadian tire on sale. To add a charger to the outboard would have costed 150 for the part and about 90 labour to install. We opted for solar as the motor was older 93 and only a 2 stroke.
The solar charger works great, it is a trickle charger, but not entry level, there are 5 watt chargers, this one is 15 watts, so it charges quicker. It will charge on cloudy days(not as good but will keep the battery topped off)
They can be kinda bulky and small boats may have difficulty with space.