46 CFR § 185.720 - Weekly maintenance and inspections.
The following tests and inspections must be carried out weekly on a vessel:
(b) Each rescue boat engine must be run ahead and astern for not less than 3 minutes, unless the ambient temperature is below the minimum temperature required for starting the engine; and
(c) Each battery for rescue boat engine starting must be brought up to full charge at least once each week if:
(1) The battery is of a type that requires recharging; and
(2) The battery is not connected to a device that keeps it continuously charged.