Only time I have heard of having to run a cranking type battery is on the older Mercs. I had a 1984 150 Black Max that I had to use a cranking type battery. I am having trouble see what a AGM starting battery would hurt running it on an alternator w/ regulator. I ran a Optima trolling 1000amp battery on my suburban for over 10 years. Never had to put an alternator on it neither.
“The world will not be destroyed by those who do evil, but by those who watch them without doing anything” Remember what He has done and remember that He is not done yet! GOD IS GOOD