Re: 1974 johnson 85hp cranking amps
I've got basically the same motor as you with a similar size battery and it works fine. I would think that you have plenty of battery for that motor. Maybe you've got some resistance in your power circuit that is robbing voltage from the starter motor. I'd look at your power connections, cable lengths/condition, and solenoid. Also, maybe your starter has issues. You may want to check the brushes, clean the commutator and check the bearings. Additionally, (obviously) make sure the battery in question is in good shape.
