It might be fun to get a comparison of what you would consider your average, and your best, cruising speed in your boat. This will require some honesty to get a true, reliable picture. I am thinking of what you would be able to replicate on a fairly regular basis, based on your knotmetre reading (trying to exclude tidal currents, etc.), not counting surfing down waves, etc.
I didn't find the right solution from the Internet.