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Old 23 October 2013, 14:37   #11
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What WOT RPM did you get with the 17k ??
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Old 23 October 2013, 14:51   #12
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What WOT RPM did you get with the 17k ??
Really canīt remember .. these tests are a year ago and the SR is sold now ..
sorry ..
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Old 23 October 2013, 16:11   #13
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I tried a 17" Ballistic on my 5.4 with a 90 Yamaha but was not very impressed by the performance .
I changed back to an 17" Yamaha K series prop which worked for me best on the SR .
The Ballistic is now on my Buster XL with F100 where it performs excellent !
Perfect whole shot , revīs with 6000rpm , 4 persons on board & tube or waterski no problems.
Yes prop testing is black art...You never know what will happens...will test i anyway.

You sold the SR, are you serious ?
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Old 23 October 2013, 16:49   #14
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Bear in mind the max recommended operating rpm for a Yam 90 2 stroke is 5500 rpm. I hit 5500 RPM with a 17k on the 85 Yam/SR5.4 (same motor bar premix)
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Old 23 October 2013, 19:02   #15
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Bear in mind the max recommended operating rpm for a Yam 90 2 stroke is 5500 rpm. I hit 5500 RPM with a 17k on the 85 Yam/SR5.4 (same motor bar premix)
Same motor on my Attaque 5.3 also tops out at 5500 with 13x17. Cruising speed is better than the 15 it came with (though obviously you lose a little holeshot). Will be interested to see next season how changing the height affects thing. 34 knots is current WOT on flat non-tidal water.
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Old 24 October 2013, 02:54   #16
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Revlimiter ?

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Originally Posted by Nos4r2 View Post
Bear in mind the max recommended operating rpm for a Yam 90 2 stroke is 5500 rpm. I hit 5500 RPM with a 17k on the 85 Yam/SR5.4 (same motor bar premix)
Does anybody know where the RPM-limiter comes into play on a Yamaha 90 ? Some people say 6000, others 5800 rpm.
One ex. racer told me that you should aim for 5800 rpm for the 90 AETO.

My top rpm at WOT so far is 5700. The prop was a Solas Titan SS 13 1/4 x 17 and the rib is an SR 4.7. Topspeed 40,5 knots. The Avon does 42 - 43 knots with the 12 5/8 x 21 alu at 5200 - 5300 rpm so the search goes on.

Still testing for the perfekt prop...
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Old 24 October 2013, 14:05   #17
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I always thought it was. 6000 RPM, but I will try to find out.

If you are operating above 5500RPM, you are just burning fuel, unless you have had the engine race prepared to pump out over 110 HP, then you will be revving harder. It's unlikely most on here will blow a Yammy rev limiter but you will know when you have, the rev limiter comes on at 2000RPM in idle and going ahead at all but min RPM is impossible, accompanied by a very strange misfire. On the older engines with the wired CDI it was an easy fix as you would disconnect the wire and tape up the connector. It was always disconnected on a race engine.

At Mitsui in the late 1970s early 1890s they experimented with NOX and the carbs froze, the 85hp yam hit well over 10000rpm and was only stopped by pulling the fuel line as it became a compression firing engine at that speed. After it was stripped, there was no damage discovered.
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Old 24 October 2013, 15:35   #18
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For what it's worth the spec sheet I found for my 85AET the "max rev range" is 4500-5500.
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Old 24 October 2013, 16:05   #19
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The 4500 lower end was for use with displacement craft, such a barges or houseboats but I've never seen one. This was because a hole shot was not required but a higher thrust was. Some of the prop diameters changed for displacement or deep very hulls.
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Old 24 October 2013, 16:52   #20
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The 4500 lower end was for use with displacement craft, such a barges or houseboats but I've never seen one. This was because a hole shot was not required but a higher thrust was. Some of the prop diameters changed for displacement or deep very hulls.
Yeah, still not a good idea to prop one so it runs over 5500 rpm though.
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