Marin, I think the GB in the original story had an older model radar on board.
You can have all the visibility and radar on board, but if you don't turn around and check or look at the screen it does no good.
When we are at our higher cruising speed we are doing about 27 knots. That's approx 30 mph. Many times fishing boats and runabouts will see us coming, and pull out ahead of us. They think they will not have to deal with us. Most never look over their shoulder. They don't usually answer radio calls, and they don't look back. Moonstruck has duel air horns, but many don't hear that. I will not pass them without their knowledge, but will fall in behind waiting for the first opportunity to get around them. If they will slow, I will too and give a good pass. You can imagine the surprised looks on their faces when they finally turn and see that big bow behind them. Some will do some crazy things. I will motion for them to slow. Most won't, so I wait for a wide enough place to go around them. Most guys in runabouts have never been passed by a cruiser before.