Nearly all sailboats sail faster with some angle of heel, and here's the Big Daddy of the sailing clinometer line. Measuring in at 6.5" long, this unit is easy to read from a distance.
Choose a vertical mounting surface that's visible from the helm, and use a fixed horizontal surface on the boat, draw a parallel line to that surfact to ensure that the clinometer reads "0" when the boat is flat. No tools are required as it includes pressure sensitive.
Sail a smaller boat? Check out the smaller versions on our "Neat Stuff Under $10.00".