Compact battery for a 12' boat. Charging advice required.

[Stuck]

In my tinny at the moment I've got a normal car battery (about 380cca) to run the navigation and anchor lights plus a small sounder. What I'm looking at doing is replacing the car battery with one or maybe two smaller 12v batteries like these, 7AH 7 AMP HOUR BATTERY AGM SLA UPS ALARM RECHARGABLE 12 VOLT 12V + BONUS | eBay (http://www.ebay.com.au/itm/7AH-7-AMP-HOUR-BATTERY-AGM-SLA-UPS-ALARM-RECHARGABLE-12-VOLT-12V-BONUS-/110920474823?pt=AU_Car_Parts_Accessories&hash=item19d36020c), as they would be a bit more convenient in both size and weight. My question is would it be OK to hook these up to the outboards charging circuit which is rated at 6 amps ?. The motor has no electric start so theres no need for high amperage delivery.

Thanks,
Anthony.

[slug_burner]

In my tinny at the moment I've got a normal car battery (about 380cca) to run the navigation and anchor lights plus a small sounder. What I'm looking at doing is replacing the car battery with one or maybe two smaller 12v batteries like these, 7AH 7 AMP HOUR BATTERY AGM SLA UPS ALARM RECHARGABLE 12 VOLT 12V + BONUS | eBay (http://www.ebay.com.au/itm/7AH-7-AMP-HOUR-BATTERY-AGM-SLA-UPS-ALARM-RECHARGABLE-12-VOLT-12V-BONUS-/110920474823?pt=AU_Car_Parts_Accessories&hash=item19d36020c), as they would be a bit more convenient in both size and weight. My question is would it be OK to hook these up to the outboards charging circuit which is rated at 6 amps ?. The motor has no electric start so theres no need for high amperage delivery.

Thanks,
Anthony.

It will come down to how long you run your motor for. I think that 6 amp charging current for a 7 amphour battery is a bit high but it will work. I suspect that 6 amp is probably a short circuit current. I think you will be ok, it will come down to how much use vs charge, may have to do the occasional top up on a charger.