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Prop Selection Woes
Hi all
After some guidance on prop selection fine points
Currently have a Gemini 550 with a 135 Hp evinrude fitted.
Prop is a cupped 14 3/4 x 17. (Evinrude SST)
Performance - WOT is 5000 rpm giving 38 knots with 3 people and 6 tanks, or
35/36 knots with 5 people and 12 tanks. (4900 rpm in this case)
Running this through a prop calculator give a very low slip of between 5 and 11 percent depending on load.
My only problem with this is WOT is given as 5250 to 5750 rpm. Since I cannot get the motor to rev to this range I am wondering if the boat is fundermentally propped wrong or should I be satisfed with the choice of prop I have
If I was to change props should I be looking to decrease dia to allow it to spin to full revs. looking at buying a SS 14 1/2 x 19 non cupped prop as an alternate. Do people think this would be a good choice, or more likely to be very similar overall.
Boat is used for diving. Usual load is 4 divers and 14 tanks, or 5 divers and about 10 tanks.
Boat currently criuses at 28 to 30 knots (3900 to 4200 rpm) with nominally 11% slip range and I am happy with the hole shot and fuel economy. Am uncertain about the motor not reaching WOT range in practice for the most part.
All thoughts appreciated
Matt
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