[wilf leek]

65 Amp alternator should cope easily with your load, it does for me.
I suspect it is not charging properly - could be a diode or two out, maybe worn slipring brushes etc.

Do you get 14.3Volts across the battery (most elec loads off, engine running above tickover)? that's the voltage you want to see, it means things are charging nicely.

HTH