AGM Batteries and Yamaha F15

Hope some of you folks can help.

I can't seem to get a clear answer whether the rectifier/regulator on electric start 15HP Yamaha F15 will charge AGMs in all conditions with adequate protection for an AGM battery against overcharge.

Second part of the question is whether the alternator and or regulator are protected from frying while charging a heavily discharged AGM.

I am a novice to outboard motor electrics and may be asking the wrong questions here but I am trying to be sure I make the right decisions. I've been told AGMs work fine with the F15 setup and I have been told use only lead/acid batteries.

Any input will be helpful

[boats.net]

Yamaha does not recommend maintenance free sealed or Gel Cell batteries because they may not be compatible with Yamaha's charging system.

Thanks for the response.

What is it about the charging system on small Yamaha outboard with electric start that would make them incompatible with AGM batteries? Just looking for an easy explanation of the general issue with these motors and maintnance free batteries.