I have ordered a Whirlwind GA200 prop for my O-320 (160 hp) RV6A. Whirlwind gives an option of 70 or 72 inch blades. Any opinions on what blade length I should get and why?
The blades are the same except for length. As an update, here is a reply I received from Whirlwind.
"Regarding the diameter, the larger diameter might climb slightly better, but
the 70" will be faster at higher RPM. Not really a night and day
difference."
Might think about resale value. Someday you might want to sell and there are many more -360s out there where 72" is the norm. And I bet the 72" will work fine on your -320. (I know it will, because I ran a 72" 200RV on mine for a year or two.)