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Old 26 August 2004, 11:32   #1
Simon B's Avatar
Country: UK - England
Town: Leicester
Boat name: Vixen
Make: Ribcraft
Length: 6m +
Engine: Suzuki OB 175
MMSI: 235071839
Join Date: Jun 2004
Posts: 1,621
WOT propping band

Well the saga continues, can anyone add to the general propping guidelines I sort of understand already;If the WOT is 5000 - 6000 should I aim for the full 6000 or mid range (5500)?

Our theoretical options are;
13" 4 blade giving 6000 RPM
15" 4 blade giving 5500 RPM

My personal inclination is toward the 13" to give some RPM in hand if it gets a bit rough or our pay load goes up. Trouble is I've not done that much rough water handling in the boat as is so dont know how much RPM we are losing at the moment. Wasnt getting much over 4700 last time in moderate swell at Plymouth.

New boat is here, very happy!
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Old 26 August 2004, 11:49   #2
Country: UK - England
Town: Bucks
Boat name: Spare Rib
Make: Zodiac/Bombard
Length: 6m +
Engine: 90hp Yamaha
Join Date: Feb 2003
Posts: 157
Dunno if this helps but we bought new Yamaha 90 last year with 13.25 x 17 prop and couldn't get over 4100 rpm (WOT range is supposed to be 4500-5500). We dropped down to 13.5 x 15 and get 5100-5200 easily and if it's really flat 5400. We also have 13.75 x 13 which gives great acceleration for skiers/watertoys but top end speed is poor. So the 15" pitch seem the best compromise. I'd say you want to get more than half-way into the WOT range but not worry if you don't hit the max.
Tim Spring
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