I have an Icom M45 VHF radio on my 20' runabout and although the radio
itself is great, the little built-in speaker is very nearly worthless
when I'm underway. It's loud enough at the dock but I can't hear a
thing while I'm moving, even if I sit down behind the windshield. This
was driving me nuts until a friend suggested getting the Icom SP-24
external speaker. This thing costs almost $50 which I thought was nuts
but he had put one on his boat and it seemed to work well (he has a 502)
so I went ahead and got one (from Consumers online marine - I think).
It really makes a difference. I can really turn the volume up loud
with it and actually hear the radio. With the built-in speaker it would
just distort. It is expensive, a little big and hard to find but it has
made my VHF radio a lot more useable. I still think the only thing that
will let me really hear the radio clearly while under way is a headset -
but it would give me a funky headset tan.