One would think a sailboater would always be the boat being passed, thus signaled for passing by faster vessels. Truth is, in Narragansett Bay there are typically more sailboats on the water than power and with my relatively larger diesel, especially when navigating tight waterways, we power much faster then them.
I use the VHF sometimes when overtaking other sailboats and dottering trawlers - but rarely have I received a reply. My assumption is that they either don't have their radios on, or it's down below at the nav station (an all too common arrangement on sailboats).
Steve