Hi Michel... For long term charters in the Caribbean I would think a cell phone based system would be better. Something like this TP-Link M7350 4G LTE MiFi and two sim cards, one from Digicel from the ex-Brit islands and one from Orange for the French islands would cover it. Might even be possible to use just one sim if there is a company with a decent roaming plan.

Personally I'd had enough of trying to deal with WiFi boosters and scrambling around anchorages trying to find an acceptable signal.