Maximum power for a ship station transmitter is given in 47 CFR 80.215 - Transmitter power. Subpart (e) applies to the VHF Marine Band
(e) Ship stations frequencies above 27500 kHz. The maximum power must not exceed the values listed below.
(1) Ship stations 156-162 MHz—25W.
Marine utility stations and hand-held portable transmitters: 156-162 MHz-10W
Reducible to 1 watt or less, except for transmitters limited to public correspondence channels and used in an automated system.
The frequencies 156.775 and 156.825 MHz are available for navigation-related port operations or ship movement only, and all precautions must be taken to avoid harmful interference to channel 16. Transmitter output power is limited to 1 watt for ship stations, and 10 watts for coast stations.