6mph
Look up the link below and add your boat info to part 5.The following note is added to the free program"The material here is taken from an article by Dave Gerr NA in Sail (February 2001. pp. 81-84) entitled Sailing Screws. To really understand the numbers calculated below you should consult this article or his book Propeller Handbook. A note on the Maximum Sailing Speed calculated below:This is also from Gerr's work. He has determined that the classic formula for Hull Speed ( 1.34 Sqrt(LWL) ) does not always apply, the 1.34 is not a constant, leading to, in some cases, much higher speeds. However, Gerr observes: "For instance, a boat with a DL or 80 might have a SL multiplier of 2.11, but it couldn't achieve that speed under sail unless it had not just sufficient sail area, but the stability to stand up to such a sail area in the wind strengths needed to deliver the required power. Not an easy task!"To use this form, select a boat, enter a Horsepower and Prop Type."The result for your Hunter 170 was 6 mph. I did enter my boat for the 8 hp I have and the results were very close. In my case the 8hp powers the 22 footer faster than hull speed. This summer I will be going to a 6hp and expect to loose .7 mph. Be interesting to see the results.Is your boat really as fast as stated in the program? Good luckJohn