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Author Topic:   New prop size advice needed
msullivan006 posted 04-09-2003 09:21 AM ET (US)   Profile for msullivan006   Send Email to msullivan006  
Need to buy a new prop without having solid reference points for performance of old one due to hub slip. Boat is 1993 O17-OUTRAGE-I; the engine is 1993 Evinrude 100-HP V-4, strong and low hours. Original prop is 13x19 aluminum. General use will be 2 people, not much added gear, probably just under 2000 pounds including full gas and passengers. WOT is not likely to be used often, more frequently will be in mid-ranges, with preference for a pretty good hole shot and ability to pull one skier pretty well. First impressions of the 13x19 were pretty good, but I think it was having a bit of a hard time getting up over 5000 RPM -this is not based on good runs, just brief run up when it seemed safe in a 10MPH speed zone.
I am down to [Michigan Wheel?] Vortex aluminum prop as first choice, and probably either 13x17 or 13x19. Vortex literature specifies this is a cupped prop, and I am guessing that the original 1993 prop is not cupped, so that would suggest leaning to the 13x17 to me. Eventually I might go for one of each with the replaceable hub, but only one fits in this time. Which should it be? (best guess, this is all of the data before I need to get something).
Thanks
Mike
tbyrne posted 04-09-2003 11:23 AM ET (US)     Profile for tbyrne    
It has been my experience (both with a Powertech prop and a Stiletto) that SS props will turn somewhat lower rpms than the same sized aluminum prop due to their greater cupping. I think you need a 13 x 17 cupped prop.
Bigshot posted 04-09-2003 02:36 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I run a 13 1/4 x17 alum on my 90hp and get about 5300 on a good day. That should be a great size for your 100hp.
Sal DiMercurio posted 04-09-2003 07:44 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Don't get anything until you get a tach on that engine.
From what it sounds, you really don't know how many rpms your twisting & thats the most important part when buying a prop.
What is the recommended rpm range for that engine ?
Always prop the engine so it reachs it's maximum recommended rpms with a normal oad on the boat & trimmed out.
The reason to do this is, if you put a bigger load on the boat, the engine wont have to struggle to carry it.
You don't have to run her at wot, just make sure she can reach it's max rpm range.
My guess would be a 13 x 17 but without a tach, your driving blind & don't have the slightest idea what she's turning.
You can't tell by ear.
Sal
msullivan006 posted 04-10-2003 08:46 AM ET (US)     Profile for msullivan006  Send Email to msullivan006     
Thanks Sal,
I fully agree with the need to target the RPM's. I do have a tach, and my only problem is that I don't have good prop to set the baseline with. That's why the request for best guesses from you guru's. From everything so far, it looks as if a 13 1/4x17 will be in the range, perhaps a tad low on pitch. If so, it will make a fine ski prop and then I can get a 13x19 blade for the Vortex hub for cruising if it seems to need it. I didn't want to make the first purchase something that wouldn't be good for either of these chores. Once I get underway, the tach and new GPS will fill in lots of the blanks. I'll be back with new questions at that point ;-)
Mike
Bigshot posted 04-10-2003 10:56 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
My 115 would barely swing a 19 to 5300 so your 100 will be fine with a 17". If you hit 5500 on the nose or a tad higher, have it double cupped which will make it an 18" and dropp you 100-200 rpms.
Tom2697 posted 04-11-2003 01:24 PM ET (US)     Profile for Tom2697  Send Email to Tom2697     
I am in the same boat as you, figuratively anyway. However, I found a good website that provided some good info. You might want to check it out....

http://www.rundquist.com/how_change_pitch.htm

BKANE posted 04-21-2003 08:10 PM ET (US)     Profile for BKANE  Send Email to BKANE     
I am in the same boat actually, 17 OR but i have a 115 and a 13X19. Did you switch props yet? I was hitting 5000RPM and 43 Mph WOT. Not worth complaining about but can I do better with a diffrent prop? BK
Sal DiMercurio posted 04-21-2003 09:04 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Bkane, 5 grand is pretty low for that engine.
If i'm not mistaken, it's rated at 5,600 rpms.
I suggest going to a 17 pitch, acctually a 16 pitch would put you right at 5,600 , but they don't make a 16p for that engine.
Are you trimmed out max & still only 5 grand ?, if so, you might concider raising the engine a hole or 2.....sure seems awfull low on rpms.
Sal
msullivan006 posted 04-30-2003 05:41 PM ET (US)     Profile for msullivan006  Send Email to msullivan006     
Hi BK,
I have not got the new prop yet, nor even gotten the boat ready for the water :-(( However, that is partly because of a side trip to St. John, so all is not negative. I'm going with a Michigan Vortex aluminum cupped 13 1/4 x 17 on the OR with 100hp. That is two full steps down from your 19" stainless, if everyone is right that the stainless ridigity is equal to another 2" or so pitch. If mine is good, you should probably be one step up with the 115 - only missing info is whether mine really is good. Now that I am back, I figure I have at least 2-3 weeks of tinkering -doing the new gear like the fuel flow guage, radio, etc. etc. I'll keep you up to date.
Mike
jimh posted 04-30-2003 08:04 PM ET (US)     Profile for jimh  Send Email to jimh     
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