For a more accurate speed reading, once you're going along at a good clip,
reset the average speed and let it run for 5 or 10 minutes. The long-run
averages seem to be much more believable than any short term fluctuations.
When I think I'm really hauling, I reset the average speed. On my P19 on
lakes (i.e. no current) the average almost always converges on our
theoretical 5.5k hull speed, though I did have a 10 minute run a while back
where I got over 6k for that time period.
If any of you have found a good way/place to mount the GPS II or similar
GPS, I'd like to hear it. I had mine in a dash bracket velcroed to the
cabintop, but I would have lost it on multiple occasions if the power plug
didn't fit so tight.