1998 2300sc Battery Charging problem

[trc41]

I have a 5.0l 220hp mercruiser with 2 batteries. Not getting a charge, is there an in-line fuse or breaker that may be causing this or is it probably the alternator?

[shrew]

Do you have a battery charger? Do the batteries charge with the charger or do neither charge the batteries? Have you tried putting a battery on another charger to see if that makes a difference? How old are the batteries?

[trc41]

Both batteries charged to full