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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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Old 10 August 2018, 14:38   #8
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4 blade prop

I would look into 4 blade props for extra thrust as you will need it.

If you can get a stainless steel prop, it will be more efficient and you will get more power pushing you forward.

Solas doesn't make 4 blade stainless as far as I can see, but they do make a 4 blade aluminum that is for heavy loads. Maybe a 9 or 10 pitch in the 4 blade aluminum would do the trick. You can contact Solas and they might have a better idea of what would work for your situation, but having your current max speed, max rmps, and load will be very helpful information for them when calculating the best prop for your situation.


I also have a 15 hp 2 stroke merc and I am looking at props for my 3.3M sib.

My current prop is 9 in 9 pitch. I just bought a 9 in 10.5 pitch 3 blase aluminum prop that should be ok to handle up to 1,000 lbs.

You really need to get an induction tachometer to see how aggressive you can go without damaging your motor. They are easy to install. You just wrap the wire around the spark plug wire. Dirt simple.
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Old 10 August 2018, 14:49   #9
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Solas do make 4 blade stainless props (I'm running one meself) whether they make them small enough for the OP is a different matter. Steel Developments are the people to speak to.
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Old 10 August 2018, 15:08   #10
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Solas do make 4 blade stainless props (I'm running one meself) whether they make them small enough for the OP is a different matter. Steel Developments are the people to speak to.
They do make 4 blade solas, but not for 2stroke 15 hp mercury with 8 splines

What are some other prop manufacturers that are on the cheaper end that I can check out?
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Old 10 August 2018, 15:59   #11
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Originally Posted by devilfishMN View Post
They do make 4 blade solas, but not for 2stroke 15 hp mercury with 8 splines



What are some other prop manufacturers that are on the cheaper end that I can check out?


Hmm! "Cheaper & props" aren't usually found in the same sentence, Mercury is the obvious choice but I'm assuming you've already looked there. Michigan Wheel might do something. I think size is the issue, stainless props are aimed at the performance end of the market & I'm not sure if you'd actually gain anything by putting a stainless prop on a small heavily loaded engine.
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Old 10 August 2018, 16:29   #12
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When I propped my engine I looked into SS I was told I would get about 5% more out of it insignificant for my 25 hp and certainly won't help you out with the 15 hp IMO you need 10 hp more to achieve performance you might just sort it with 5 hp more
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Old 11 August 2018, 05:10   #13
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Ron Hill makes props for those smaller engines, his props are very low quality though and usually require a fair bit of work to make them run properly. If you're prepared to spend the money you could try Winrace, one of the top names in performance props but mostly for racing use
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Old 11 August 2018, 07:18   #14
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Ron Hill makes props for those smaller engines, his props are very low quality though and usually require a fair bit of work to make them run properly. If you're prepared to spend the money you could try Winrace, one of the top names in performance props but mostly for racing use
Hi all

I run a 13p michigan Ballistic prop on my 20 hp and the hole shot is instant 3 to 4 secs to top speed 24mph .
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