Re: crancking batteries for a 2009 HO 200hp.
Hey atello, welcome aboard!!
A couple of things . . . I moved this over to the Electronics section to try and get you some more generic help. This is not really motor specific.
I have a very similar combo of electronics although I have an I/O . . . 1000 watt system, GPS, depth sounder, two batteries.
I am sure the boat has a battery switch. Those cranking batteries will be fine depending on how you use them. If it were me, I'd start each day with two freshly charged batteries (trickle or quick charge at home). I'd have the battery switch on Both for the first extended run of the day to give both of them a fresh charge after starting. At my first stop I switch over to #1 or #2 battery depending on what day of the month it is. Odd days on the calendar, I use #1, even days I use #2. Then I go about my day knowing that if I sit at anchor with the stereo running etc. that I always have a fresh battery there if I need it to start and get home. I have two combo style start/accessory marine batteries. If I run the stereo for a few hours a single battery will crank a little slow. If I am boating for a couple of days in a row, I also switch over to both on the battery switch for the last ride of the day. This way I have two fresh for the next morning.
As long as you can get the motor started, and the alternator is charging properly, you should not get to the point where you have any trouble with her staying running. If the alternator failed you can drain the battery while running and then be in a world of hurt, but that starts with the alternator and coupled with weak batteries.
I would be especially cognizant of any changes that you see throughout a season. If she cranks slower than she did last trip, then maybe you have a battery getting weak. With the abuse of boating and the non-daily use, I only get two or three seasons out of a battery . . .
