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Old 26 April 2012, 13:10   #11
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Country: Germany
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Quote:
Originally Posted by njensen View Post
what is fast ?

I get 31-33 knots @ 5200 rpm with a 90 HP E-Tec on my SR4.7 (15" alu prop).
Inititally i tried a 17" alu prop but it only gave me 4900 rpm wot.
33 knots is fast enough for me on a 4.7m rib...
Hi ,
Is there something wrong with your setup ??
That 33 knots are fast enough is one thing but I would assume that the max speed with 90hp ETEC on the SR4.7 would be higher !
My old Yammi 90 2stroke pushes my SR5.4 with big Osprey console , 90 liter tank + myself with appr 120kg up to 38knots (GPS) with a standard Yamaha aluminium prop 19 pitch .
Cheers - Jürgen
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Old 26 April 2012, 15:18   #12
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Quote:
Originally Posted by Bushrider

Hi ,
Is there something wrong with your setup ??
That 33 knots are fast enough is one thing but I would assume that the max speed with 90hp ETEC on the SR4.7 would be higher !
My old Yammi 90 2stroke pushes my SR5.4 with big Osprey console , 90 liter tank + myself with appr 120kg up to 38knots (GPS) with a standard Yamaha aluminium prop 19 pitch .
Cheers - Jürgen
About right I'd say for a commercial 5.4 with a 90. I have A tohatsu 90 that gets 31ish a yammie 80 that gets 32. The larger merchant gets 35 fully trimmed up. I wouldn't expect to much more and hold on tight for that chine walk
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Old 26 April 2012, 18:18   #13
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Country: Denmark
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Speed is not so much about HP. It's more related to prop, gearbox, drag and the engine max rpm.

Since my engine is turning 5200 rpm wot @ 32 knots... it can't be too wrong. According to my calculations it gives a prop slip of around 0% (and 5200 is max for the 90 HP)

I might be able to raise the engine 2 holes, and turn a 17" prop instead. That would give around 36 knots assuming no slip. Actually i'm going to try to raise the engine, but that's just to optimize fuel consumption.

My old Suzuki Dt65 gave me 36 knots using a 16" alu prop and 5800 rpm.

I really don't care about top-speed, i need acceleration and fuel performance.
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Old 26 April 2012, 19:36   #14
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Can anyone give me a rough estimate of how much fuel I would burn with the twin Yam 40's in this thread? Still mulling a Sr5.4....and I could do with thet win redundancy up here....but have no clue as to the fuel costs.

Good to hear it planes ok with one.
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Old 27 April 2012, 19:21   #15
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it's a guess.... 1.3-2 liter per NM...

my SR4.7 + 65DT Suzuki used about 0.9-1.1 liter per NM.
with my new E-Tec 90 HP it's more like 0.6 liter per NM.
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Old 28 April 2012, 04:18   #16
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3ltrs per nm
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Old 28 April 2012, 04:24   #17
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Quote:
Originally Posted by benjytaylor
3ltrs per nm
I travel approximate 10nm every day on the searider's- 1. 4m searider yammie 40 : 15ltrs. 2. 5.4SR merc 75 4S : 8- 9ltrs 3. 90 twatsoo : 20ltrs. 4. 80 yammie 2S 18ltrs.
I hope that helps.
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Old 28 April 2012, 04:25   #18
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Sorry forgot to mention that's cruising @ 20-25knts for about 8nm and the other 2nm @ 6knts
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