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Old 26 May 2010, 15:05   #1
Country: UK - England
Town: bournemouth
Boat name: ribbed for pleasure
Make: bwm
Length: 5m +
Engine: outboard
Join Date: Mar 2010
Posts: 32
prop sizing help

hi all im looking for some advice on prop sizing i have a 18ft bwm with a johnson v4 85 hp engine i use the boat for a bit of dohnuting and fast crusing what you recomend?

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Old 26 May 2010, 15:09   #2
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Country: UK - Scotland
Boat name: imposter
Make: FunYak
Length: 3m +
Engine: Tohatsu 30HP
MMSI: 235089819
Join Date: Sep 2005
Posts: 11,094
Originally Posted by steveplumber View Post
what you recomend?
I recommend you post the following info so the prop gurus can help you:

Maximum recommended engine revs (or range)
Current maximum revs at wide open throttle (WOT)
Current maximum speed at WOT
Gear box ratio for your engine
Current prop size DIAM x PITCH, plus no of blades and Ali or S/S

If you are happy with speed / hole-shot etc?
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Old 26 May 2010, 16:53   #3
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Country: UK - England
Town: Fareham
Length: 6m +
Join Date: Sep 2003
Posts: 7,855
I had a BWM Deepsea 17 with an 80 Yam and then a 90 Merc on the back and the best prop that I found was 13.75X17" alloy for general purpose with a 15" spare that I could also use if I had a heavy payload and needed some grunt.

I did a lot of experimenting with Stainless V's Alloy props and found virtually no difference in performance between the two. At the end of the day I chose the Alloy ones because they're cheaper to buy and if you hit an underwater obstruction then the prop is likely to take the impact protecting the gearbox a little.

Looks Slow but is Fast
Member of the ebay Blue RIB cover club.
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Old 03 June 2010, 05:00   #4
Country: UK - Wales
Town: west wales
Make: humber destroyer 5m
Length: 5m +
Engine: 90 yamaha
Join Date: Apr 2010
Posts: 202
Assuming johnson and evinrude props are the same (downhilldai please advise) I have a 15'' and a couple of 16.5'' plus a 17'' all in stainless ,one of which may be suitable.
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Old 09 June 2010, 07:30   #5
Country: UK - England
Town: Eltham
Make: XS Ribs
Length: 5m +
Engine: Opti 150
Join Date: Jun 2010
Posts: 18

Hello Bosun
are you looking to sell the props you mentioned?
If so what diameter and spline size are they please?
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