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Old 18-11-2009, 13:18   #1
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Outboard Prop Question

We need a new prop for our 15hp Honda outboard. The current prop is 9.5x8.625". It is on a large, heavy RIB dinghy and will get two of us on plane with some gear, but really loads down with another person or more gear and won't plane.

I have a choice of new prop pitches. Would changing the pitch allow the dinghy to plane with heavier loads? If so, should the pitch increase or decrease (I'm leaning toward decreasing it an inch)?

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Old 18-11-2009, 13:33   #2
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I don't think reducing the pitch will help. The basic problem is too much weight and the Honda is a heavy motor. I spun a prop on my 15hp Yamaha and my spare had less pitch. The only difference I saw (or heard really) was more revs and less speed at the top end. And I don't think it got up on plane as fast. Now this is unscientific and based on my perception only. Again, your basic problem is too much weight and not enough horsepower. I would not fool with the pitch as it works with the two of you and that's all that's going to be in the dink most of the time.
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Old 18-11-2009, 15:23   #3
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How many hp is your dinghy rated for? If it can take 25 and you've only got 15 you just need more motor. You might also add some Doll-Fins t/m or a similar product. They really do help.
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Old 18-11-2009, 20:43   #4
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The dinghy will take a 30hp engine, but I'm stuck with what I have. I do have Doll Fins on it already. I asked my question because when I looked at props for this particular engine, Honda lists props in several pitch sizes for it (plus 3 and 4-blade options). So I figured that there was a case for matching the pitch with the type of load the engine is working with and I might have a better choice than the prop that arbitrarily came with it.

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Old 19-11-2009, 00:02   #5
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When under the heaviest loads can it reach maximum RPM? If not, reducing the pitch will help some, but as others have said, the boat may be underpowered for the weight.
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