To find your speed over water, measure a distance of a nautical mile (6080 feet) on a chart, look at the start position, and the finish position, make sure you are going full speed when you pass the start position, and still going full speed when you get to the finish position. turn around immediately and run back up, add the two times together, then half them, then time over distance, gives your speed. However, this is mainly done on rivers, with ships on trials, and they do it up and down the river, where they have currents, either on the bow, or on the stern. Not so accurate if you have changing currents over that mile. The winds will be factored in, with the double run, you could have the current pushing your stern, and the wind pushing your bow on the first pass. The current on your bow, and the wind on your stern second pass. Which would give the same results as a week later if you did it again, and had wind and current on your stern first pass, and against you second pass, or third week, when their is no wind, and no current.
Again, you could take your speed over ground, in both directions.
As to what your speed should be, havent a clue, Kind of like the last fast car i had, manufacturers data, said top speed, 135 mph, approx, because some will go faster, and some will go slower, and if it does 135mph tops, with a 150 pound driver, it wont do that top speed, with a 300pound driver, and four 300 pound passangers (not that two three hundred pound passangers could have fitted in the back seat, but if they did, and the car didnt do exactly 135, and the manufacturer said it would do that, i could perhaps sue him.
Its like thirty foot boats, that manufacturers consider as bluewater boats, they may well be, but they will never say that, their marketing departments hint at it, They might say "enjoy a trip to Bondi Beach on our new thirty footer" but they dont say sail from new york round the horn to bondi beach on our new thirty footer" because if they did, they would end up getting sued.
