posted 04-17-2015 01:42 PM ET (US)
It is often useful and informative to give details about the propeller that was used, including the diameter, pitch, manufacturer, and model.Performance data from saltwater testing may produce better speeds than freshwater test data due to the difference in density of the water--saltwater is more dense than freshwater--and sometime from temperature of the water. Tests in cold saltwater tend to have better speed results than tests in warm freshwater.
Air temperature also affects performance, so it is also interesting to give some details of the air temperature during testing. Testing in cold low-humidity air produces better results than in warm humid air.
With my own boat, I have see a variation in top speed of about 5-MPH based on testing done in very cold air and cold water compared to testing done in hot, 90-degree air, and warm water.
Speed is always in inverse proportion to weight, so boat weight is a big influence, too. For that reason it is also informative to mention something about the added weight onboard, such as fuel volume, number of people, extra gear, and so on.