From 300' behind to 300' ahead is 6 minutes. From 500' behind to 500' ahead is 10 minutes.
Neither probably an issue with no traffic, but when you're on a busy waterway with approaching boats, it is lengthy. Often not time to clear before meeting another boat. Just all depends on what else is going on around.
To me far more complication with those going 12 knots. They put one in a situation where it's hard to pass without creating a wake. Consider approaching such a boat from behind at 20 knots. Often the choices are (A) They continue at 12 knots, we pass at 15-20, quickly but with wake or (B) They slow to 8 knots, we pass at 10-12, no wake, then speed up after passing.
We have one non trawler type that we can go around 10 knots with minimal wake, at 12-20 however we have a substantial wake, at 40 knots we have very little wake yet often people are upset if you pass at that speed. But if a boat maintains at 15 knots or so as we want to pass, our only choices are open it up to minimize wake or pass slowly creating a large wake. On the other hand if the boat being overtaken slows to 6-8 knots we can pass at 10 and give no wake.
One of the funny things is to be behind a boat which is creating a very large wake itself. The likelihood is strong then at a passing speed, assuming they maintain speed, then you're going to create a large wake.
