One thing you can do when you see a powerboat about to overtake you is to slow down to about 2 or 3 knots. If you stay at 6 or 7 knots, you're asking him to be in the low teens to make a pass. Which makes a huge wake. A knowledgeable powerboater, (they exist), will wave a thanks for letting him make a pass at a lower wake speed of around 7 knots.
Most large boats on plane at 30 knots will create less wake than one dragging it's arse in the water at 12, so he may be doing you a favour by blowing by you.
One other thing, and while it's not an excuse, it does point out some frustration that large cruisers may have. Getting up on plane uses a lot of fuel. If a large power boat owner has to do that every 10 minutes, well you can see how frustration mounts.
You might want to google displacement/transition/planing speeds of powerboats. It will give you a good idea of of you can help give a powerboater a decent passing window.
Another thing, monitor 16. While most sailboaters think stinkpotters don't use radios, most cruisers think blowboaters don't either. So someone has to be right.