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Old 05 December 2007, 07:29   #21
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Country: UK - Scotland
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Originally Posted by Cookee View Post
FYI our record run managed 9% slip,... and for those getting 3% or even negative slip there is something wrong!
At last, intelligence!


I think I'm qualifying for Grumpy Old Men today. Maybe the time of the month.
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Old 05 December 2007, 08:02   #22
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Andy, there will be a test wheel specific for each engine. The idea is that the test wheel loads up your engine to its maximum power so when fitted and run up in a test tank your engine should pull its ideal RPM (in your case 5000). It it does not then you have problems.

Chris
That's the answer I was expecting. So I guess I'm looking at a dealer to do this test then.

Still awaiting a phone call from BRP
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Old 05 December 2007, 15:40   #23
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Quote:
Most engines are designed to work within a band of about 1000 RPM at top speed anyway for instance my Etec is rated at 4500 to 5500 RPM.
Chris
You are right about most engines working within a band of 1000 revs ie. the V6 Etec 4850-5850 optimum 5350, the V4 115 is 5500-6000 optimum 5750.
(info taken from BRP service manual)

I have a Viper 17" prop WOT 6000 and a Solas Titan 19" prop WOT 5700 both seem to give 8-9% slip.

Keith
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Old 05 December 2007, 19:18   #24
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Originally Posted by Chris View Post
I think people tend to get hung up on RPM especially if your tacho is not too accurate...

Why sacrifice top speed just so you get your ideal RPM reading on the tacho?

Most engines are designed to work within a band of about 1000 RPM at top speed anyway for instance my Etec is rated at 4500 to 5500 RPM.

I find the best results are running the 18" prop which gives me a top RPM of around 5400 on the tacho. On my previous engine (Johnson 90) I found that the best results were obtained running the engine at around 5200 RPM (on the tacho) I suspect the tacho on this engine was at least 100 RPM out though so I may have only been pulling 5100 RPM.

Its more about power band than RPM.

Chris
Maybe i phrased thast badly , What I meant was that my boat was clearly overpropped when i got it . It felt sluggish at slower speeds and the motor was labouring trying to keep it on a slow plane. and only reaching 4500rpm at wot at 40mph . One pitch lower and its really lively and reving to about 5k , i just expected to get an increase or at least the same top speed not less as the motor must surely now be in its power band .
However cruising is better and lots more economical and thats what really counts for a pleasure boat.
I would like to try an alloy prop the same pitch as the stainless one I bought just to set my mind at ease , but where do you stop prop testing , finding a loan prop is near impossible and as these threads prove its a trail and error art that no one can give reilable advice on.
I have no reason to doubt the rev counter is far out
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Old 06 December 2007, 02:56   #25
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Totally agree Ian I have about 800 worth of props that I would be lucky to get 250 on ebay.
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Old 06 December 2007, 03:05   #26
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Originally Posted by kwil View Post

I have a Viper 17" prop WOT 6000 and a Solas Titan 19" prop WOT 5700 both seem to give 8-9% slip.

Keith
Keth I thought the max RPM for an Etec 115 was 5500?

Check out this spec sheet for the 115.....

http://www.llynmarine.co.uk/images/SPEC_ETEC115.pdf

it shows that the engine develops 115HP at 5000RPM hence my point about powerband.

Chris
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Old 06 December 2007, 04:34   #27
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Tell me about it - I have a couple of grands worth of props. Fortunately I got them off ebay for 500 quid.

Quote:
Originally Posted by Chris View Post
Totally agree Ian I have about 800 worth of props that I would be lucky to get 250 on ebay.
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Old 06 December 2007, 05:08   #28
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Why dont we start a post where everyone posts up what spare props they have.....

I am going to start a post and ask John to make it a Sticky

Chris
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Old 06 December 2007, 05:09   #29
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I'm interested in props 28" pitch or more, either small shaft merc hub (V6), or flowtorque.
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Old 06 December 2007, 06:09   #30
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Why the fek don't you all just invest in a Torqueshift then you can have anything you like from 14" - 32". Well, the folk with the bigger engines can.

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