A couple things to note: Small engine charging systems do not put out much current at all, and only near their rating at close to full throttle. Most sailors of small boats do not use the outboard enough and at high enough RPMs to get meaningful charging. Solar would be better.
That being said, a Sailpro model Tohatsu 6hp with extra long shaft and high thrust prop is a great motor for a 22 footer.
The Tohatsu/Nissan/Mercury (and one other brand that escapes me) are all the same powerhead. And the 4 stroke models all have very, very small low speed idle jets for fuel economy and pollution issues. Use ethanol free gas if you can get it!
www.pure-gas.org Treat the fuel with Sta-Bil and Seafoam additives, to make sure that the low speed idle jet doesn't get gummed up. I use both even on my non-ethanol gas. If you can't get non-ethanol gas, either use up your fuel quickly, or frequently change it out by dumping in the car and replacing with fresh. Maybe even more frequently than 1x month.
This should keep that 4 stroke carb happy. If not, if you continue to have trouble getting it to start or idle, a very good mechanic might want to drill the idle jet out a wee bit...
I have a '99 5hp Nissan which gets run at least 2x week on ethanol free gas, and I have not had any problems. However, this season, it's only been run once every other week or less. It's been hot and humid the past week, and I'm hoping she keeps her stellar operational record. Heck, for that matter, I hope I can get back to my regular 2-3x week sailing schedule soon!