We had the same situation as you, great service
up on deck but not down in the cabin
, and we tried several approaches. In the end, we settled on a cheap wifi
range extender from Best Buy for service
in the marina and use a cellphone hotspot for service when underway or at anchor
. Works great. The range extender is plugged in up on deck at the flybridge. It relays a signal down to the cabin
and is five bars all the time. At anchor
, our cellphone hotspot even allows streaming NetFlix and other services to our TV. Working well for us but your mileage may vary.