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Old 28 May 2015, 05:01   #1
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Which propeller?

I have a 3.3m Quicksilver inflatable which I use with a 15 hp Mercury 2 stroke. I use it for 3 mile trips across calm sea to get to an island for snorkelling with 2 adults, 3 children and an amount of stuff. It just about planes when fully loaded. I have just bought a 4.2m sib as the extra space will be really useful. I don't want to use a bigger engine as the extra weight will make it too much for me to pull up the slipway. I'll be fitting some fins to the outboard to help it get out of the hole but - and here come's the question - what propeller should I use to be able to get the greatest weight onto the plane. The existing has a 9 inch pitch. I'm not concerned much about faster speeds once planing. Thanks!
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Old 28 May 2015, 05:28   #2
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I think you'll struggle to get a 15hp 4.2m sib with 2 adults and 3 kids to plane with any propeller. You need a bigger engine or a smaller boat.
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Old 28 May 2015, 10:21   #3
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[QUOTE=davesalt;679744]I have a 3.3m Quicksilver inflatable which I use with a 15 hp Mercury 2 stroke. I use it for 3 mile trips across calm sea to get to an island for snorkelling with 2 adults, 3 children and an amount of stuff. It just about planes when fully loaded. I have just bought a 4.2m sib as the extra space will be really useful. I don't want to use a bigger engine as the extra weight will make it too much for me to pull up the slipway. I'll be fitting some fins to the outboard to help it get out of the hole but - and here come's the question - what propeller should I use to be able to get the greatest weight onto the plane. The existing has a 9 inch pitch. I'm not concerned much about faster speeds once planing. Thanks![/QUOTE

Hi

What's your total weight in stone.Had a 15hp on my Sib with 7.5 pitch prop it would plane nicely with 40 stone on board..
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Old 28 May 2015, 12:10   #4
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You will struggle to plane with that combination. We have a 4m honwave which can plane with a yam 15hp 2 stroke and 2 maybe 3 adults. It's just a tender, for use as a family boat I reckon you'd be after a 25 or 30hp.
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Old 30 May 2015, 14:00   #5
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I have a 3.8m Honwave with a 15hp Honda which planes fine with 4 adults and 2 very small children. It all depends on the size of the adults.
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Old 01 June 2015, 02:09   #6
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Our total passenger weight is about 40 stone (250 kg) and there's always a bit of stuff we have with us as well. The 4.2m I think is 35Kg heavier than our existing 3.3m. Perhaps the extra buoyancy will help it onto the plane? Anyway, I'm determined to give it a go with the 15hp and will try fitting fins and then dropping from 9 inch pitch to 8 inch. I'm also tempted and daft enough to have a go at drilling vent holes in my existing prop. When I tow my two largest daughters on a ring the 3.3m only just gets planing. It often porpoises a bit first and when it does as soon as the prop gets a little air it speeds up (the engine that is) and pushes straight onto the plane - the effect I'd be hoping to get by adding vent holes - if I get them the right size.
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Old 01 June 2015, 05:30   #7
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Hi

I would say your at the limit with engine and prop,you could try a 7 pitch prop but it's still hit or miss.

I would sell the engine and go for a 20 or a 25hp 2 Stoke would be the same weight as 20hp 48 kg.
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