Boater's Education Certificates

[SBC]

Originally Posted by jrc

By my calculations a person with average vision can read 3" letters at 172 feet so that's a pretty good rule of thumb.

distance in inches = 3 inches / tangent of 5 minutes of arc

Of course people with poorer eyesight have to come closer to read the numbers. Which means in congested high traffic areas, I should take off my glasses to maintain high speed.

What you may actually find is that the majority of folks with 20/20 or corrected vision can read the 3" bow numbers clearly at about 100-125'. I saw a clear demonstration of this in a Boating Education class. Only a few younger boaters and women are able to read those numbers clearly at 150'. Also take into account that that would be under ideal conditions, i.e. contrasting color to the hull, minimal water/sun glare/reflection, little or no steep rake on the bow, etc.

When in doubt, slowing down is always an option.