Going from 14X9 to 14X7 prop

[ris]

Got kind of bored being home and not being on the water so had my 14X9 prop changed to a 14X7 just as a test. Here is the data. This is not a totally fair test as I had 850 more pounds of people on board for the 14X7 prop test. Will redo test at a later date with just 2 of us. So here is the data from different props and one prop with two different pitches. This is with the Honda 60 4 stroke with the High Thrust motor. It is a 60 hp motor with a 70 hp foot. We used the 14X9 to do the 5800 mile loop last year. It worked just fine. It cost $50 to change the pitch from a 9 down to a 7. The 14 inch prop is aluminum and the 13 3/4 is a stainless prop.
RPM 13 3/4 X 13
2000 8 mph
3000 10 mph
4000 no data
4500 WOT 19.5 mph

RPM 14 X 9
2000 6.5 mph
3000 9.1 mph
4000 15.5 mph
5250 WOT 21.5 mph

RPM 14X7
2000 6.08
3000 7.8
3500 8.6
4000 9.5
4500 10.7
5000 12.6
5500 WOT 14.6

[Sumner]

RPM 13 3/4 X 13
2000 8 mph

RPM 14 X 9
2000 6.5 mph

RPM 14X7
2000 6.08
3000 7.8

Don't know anything about those large outboards and props but to me it looks like for someone doing the 'loop' and running most of it at below max. hull speed the 13 3/4 X 13 would be the best prop as it looks to run at or below hull speed at a lower rpm unless the outboard uses less fuel there,

Sumner

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1300 miles to the Bahamas and back -- 2015

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