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Old 30 November 2014, 03:10   #1
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More Prop advice please Suzuki DF140

Hi everyone had my Vipermax ( with Suzuki DF140) on the water for the first time yesterday at New Brighton on the Wirral. Fantastic day but it raised a prop question. I've currently got a 14x21" aluminium prop and yesterday managed a WOT 5500rpm and speed of 35knts. I realise reducing the pitch will increase max revs but should I risk going to 14x18" to get theoretically 6100revs and increase speed or is this too big a jump?
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Old 30 November 2014, 03:29   #2
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that would be about right
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Old 30 November 2014, 03:30   #3
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35 knots at those revs sounds fine. Look at the manual for that engine and see what rev range it states as top end to see if feasable. you might allready be in the ideal wot rev range so exceeeding might put too much wear and stress on engine and components.
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Old 30 November 2014, 03:39   #4
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I've read that max revs for the DF140 are in the range 6000-6200 so thought I might be able to get some more top end speed by reducing the pitch. That is right??
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Old 30 November 2014, 03:53   #5
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You are only looking to gain 500rpm, will it make that much difference to the top end?

Do you run flat out all of the time? Are you actually likely to use your extra couple of knots?
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Old 30 November 2014, 05:15   #6
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Quote:
Originally Posted by JohnnyMW View Post
Hi everyone had my Vipermax ( with Suzuki DF140) on the water for the first time yesterday at New Brighton on the Wirral. Fantastic day but it raised a prop question. I've currently got a 14x21" aluminium prop and yesterday managed a WOT 5500rpm and speed of 35knts. I realise reducing the pitch will increase max revs but should I risk going to 14x18" to get theoretically 6100revs and increase speed or is this too big a jump?
With that engine/hull combo I'm sure there is more performance to be had.
I'd Try speaking to other VM owners to see what they run...and what performance you can expect before spending out!
Once your confindent of what May be achieved ...it might well pay to get a SS prop in the chosen size,and keep your present one as a spare
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Old 30 November 2014, 05:16   #7
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that would be about right
Yeah right!...frightened of the competition!?
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Old 30 November 2014, 05:18   #8
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500 rpm off peak HP is quite a lot.
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Old 30 November 2014, 09:10   #9
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500 rpm off peak HP is quite a lot.

That's my point, peak power according to Suzuki is at 6000rpm with max of 6200. My 14x21" aluminium prop is giving me 5500, so dropping 2" of pitch should bring the rpm up. If I go stainless the only option with an OEM prop is to go 14x20 or 14x18. The 18" just seems a big jump and at 300+ and expensive experiment. Maybe just go for the 18" and have it cupped if necessary. Any Vipermax 5.85m owners out there who can help?
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Old 30 November 2014, 09:20   #10
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Ah, just spotted that it's a 5.8.

DHD has a 150 Opti on his 5.8, that'll pull almost 47knots.

Roycruse had a DF140 on his RC585 running a 21P SS prop, that would hit 41knts.

I'd expect your rig to achieve somewhere near the 40knt mark.
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