Marine electronics are not designed for continual exposure to rain and splashing. Buy the optional cover from the manufacturer that protects the front panel of the radio. Leave the cover on the radio except when needed. The radio will endure rain, dew, splash, and other water intrusions much better if protected by a cover.
Any fixed-mount VHF Marine Band radio you buy today will be a 25-watt radio and be rated for compliance with digital selective calling to CLASS-D specification. If you don't have a GNSS receiver on the boat, say in your chart plotter, or you are not interested in performing the electrical interface between the radio and a GNSS receiver, I recommend you buy a radio with its own GNSS receiver built-in and already interfaced to the DSC portion of the radio.
I have no reservation at all about recommending VHF Marine Band fixed-mount radios made by Standard-Horizon. I have been on several boats of the Coast Guard of the USA in which the boat radio was a commecial-off-the-shelf (COTS) radio. Those COTS radios were always Standard-Horizon radios. If a Standard-Horizon radio is good enough for the Coast Guard boats, it should be good enough for your boat.
I have been using Standard-Horizon radios on my boats for years. The reasons I prefer Standard-Horizon radios are:
--they have excellent user interface features, are easy to operate, and can be operated without having to read a 100-page manual;
--they offer very good compliance with DSC specification; they are usually the first brand to have many DSC features;
--they have excellent and very responsive, friendly technical support, should you need it;
--they offer a flat-rate repair at a reasonable price
--the radios generally provide very good quality, excellent features, and high reliability at a very modest price
--the transmitter modulation of Standard-Horizon radios is generally superior to many other brands
