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New SS prop - wrong pitch?
|Author||Topic: New SS prop - wrong pitch?|
posted 02-11-2004 08:55 PM ET (US)
Need help prop Gurus,
bought '99 dauntless 15 w/ 60 hp merc 2s. Max rpm on merc is 5000 - 5500 rpm.
Came with 10 1/2 x 13 worn Alu prop. Turned 5600 rpm @ WOT.
Raised motor 3 holes (now in next to highest hole - bottom of a/v plate is approx 1" above keel).
Replaced prop with SS Turbo 10 1/2 x 14. Now lightly loaded (just me w/ 8 gal gas) in cool temps (50 deg), only reaching 5100 rpm @ WOT.
I'd estimated she'd drop 400 rpm between switching to SS and going from 13 to 14 pitch. Then hoping to pick up 200 rpm from raising the merc 2 1/4", with a net rpm of 5400.
Since now I'm only seeing 5100 rpm, maybe the old alum prop had lost its shape and was no longer a 13p.
Seeing I'm at the low end of the range when lightly loaded in cool temps, should I take advantage of their trade-in program and get a 13" pitch? Or did I just choose too aggressive a style of prop....
She's the most beautiful, highly polished prop I've ever seen! just dont work none to good :)
posted 02-13-2004 08:27 AM ET (US)
When ever I have gone from aluminum to SS, I have found that the rule of thumb for determining RPM based on prop pitch is always a bit off. I think this is because of two reasons.
1) The SS prop is heavier (usually a lot) than the aluminum
2) Often times the SS props are cupped - adding to the slower RPM.
I would think you need to drop the pitch by an inch or two.
posted 02-13-2004 09:15 AM ET (US)
Thanks Brian for the response.
Jim, Big, Sal, Grey, Buck, Lhg - any thoughts?
12" or 13" pitch?
posted 02-13-2004 09:21 AM ET (US)
The only thing I would add to Brian's excellent comments is slippage. Your "worn" aluminum prop may be slipping at WOT...and the SS Turbo isn't. Sounds like the 13 pitch might be the ticket.
posted 02-13-2004 06:51 PM ET (US)
I'm not a big fan of Turbo props.
My choice would be a Stiletto 10.5 x 13
$245.00 at ....Aftermarket.
They wont exchange if it's the wrong size.
For $20 more [ they allow you to exchange ]you can get it from Overtons @ Overtons.com
posted 02-14-2004 02:00 PM ET (US)
Thanks Steve & Sal,
Yes Steve, I thinks you're right about the old Alum prop slippingfar more than it should have - lost its cup I suppose!
Sal, the exchange program on the Turbo was one of the reasons I went that route over the Stiletto. I'd spoken with Cathy (I think she said she was the head of tech support for both Turbo & Stiletto) and she said the Stiletto was a good SS OEM replacement prop. The Turbo was very similar, but finished much better than the Stiletto. I specificly asked if I was doing myself a disservice by going with the Turbo (higher performance? more cup?) and she replied "not at all!"
With her input and since I'd found the Turbo for less ($217 incl shpg - Dan's discount props) I went that route.
Thank you guys for the prop scoop - I'll change the 14" in for a 10 1/2 x 13"
Sal, in the back of my mind I still question if the Turbo has more cupping than is good for my setup.
posted 02-14-2004 04:07 PM ET (US)
Soup, you wont find a better finish then on a Stiletto, it looks like a mirrow but it's not the finish that counts.
As i'v said, i'm not a big fan of Turbo props because just about every person I know that has or had them, really wasen't all that sure if they liked it or not.
I have never run one on my rigs.
I'm sure your aluminum prop is worn down to much less then it is marked allowing more slip then it should.
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