u/lowflash,

I follow you. This is why I label my assumptions. Corrected to understand RC boat is set and you're focused on mark boats. Roger that you have familiarity and experience with Pelican cases for go-kits and you're licensed.

I'm very fond of the Motorola powered speakers but there are alternatives. I see them in public safety (police, fire, EMS, tow) and commercial duty. I have one that has outlasted two personal trucks and is nearly forty years old and works like a champ. The amplifier is linear so the sound is good. You adjust volume with the volume control on the radio so there is no training. The beefy speakers are here. The waterproof MLS-200 is about $70US. I did a quick look for detailed documentation without luck. If I recall, the speaker cone is plastic so should take a direct hit from a wave and just shrug off spray. A local commercial radio shop my be able to help you with documentation or you can reach out to Motorola directly. You may found power over audio on some speakers but Motorola will have a combiner.

You might want to add a speaker to your RC boat so people in the cockpit and/or flybridge can hear better. If you hook up two speakers you'll want to do a little impedance matching for best performance. A little audio transformer from DigiKey and five minutes with a soldering iron or white crimps will do. White crimps (the tiny ones) are available from DigiKey and Grainger and elsewhere.

Here is a search for waterproof marine handhelds from SH and Icom. I remember that some radios inject a subaudible tone into the speaker (again plastic material) that causes it to vibrate and shed water droplets). I leave tracking that down to you.

People use speaker mics in all kinds of duty. One trick is to run the cord inside clothing to reduce snags. The remaining problem with handhelds is that they themselves risk snags. I recommend you find a case or attachment so users can thread a belt through the case. A clip is not enough. You will eventually lose a radio. You'll also have radios in water at the bottom of the mark boat. Waterproof radios will be okay but the mark boat crew won't be able to hear anything. When an antenna gets caught on something it usually breaks the connector off the handheld. Buy a couple of spare radios.

If you are committed to handhelds I'd still go with speaker mics. Your call. You'll want a charging station for handhelds convenient to where RC crew pick up the Pelican cases. Set up tags on the handles that show the radio is in the charger and needs to be picked up. Note that the fancy handhelds with GPS and DSC such as SH HX-8XX do not have the battery life to make it through a long race day. Every smartphone has GPS apps including free ones to directly read lat and long. Better yet would be planning in advance and transferring a GPX file from a planning tool (I use OpenCPN) to a nav tool on phones (I use Aqua Map by preference) with waypoints set for planned marks. You'll still want lat and long in case you have to move the course for a wind shift. The waypoint approach avoids transcription errors when working from paper. I do not recommend Navionics despite its popularity. I have more demanding nav needs than you do but shortfalls may still bite you.

The more I think about it, the more I tend toward fixed radios in the mark boats. Mount them in the console if you have a console, in a Pelican case if there is no console. Again, your call.

This is a fun exercise.

73 es sail fast de dave KO4MI/MM (E) S/V Auspicious