Steve21slx
Well-Known Member
As I search for a new prop or a spare prop I ran across this reply to a question on the yamaha website. Anybody do this?
Why does my boat seem to lose top speed on hot humid days?
On hot humid summer days the air is less dense which causes the engine to run richer and be slightly down on power. To the contrary on cold winter days the air is more dense which causes the engine to run leaner and have more power. If you are concerned with making sure you get the peak performance out of your motor year round it may be necessary to use two different propellers depending on the time of year. To compensate for the loss in power on hot humid days you would need to go down in pitch and on cold days up in pitch. For example you may be running a 26" pitch propeller in the summer and a 27" pitch propeller in the winter.
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