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| Prop Padawan! http://mudmotortalk.com/mmt_v2/viewtopic.php?f=41&t=9447 |
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| Author: | Caleb W. [ Sat May 01, 2010 11:38 pm ] |
| Post subject: | Prop Padawan! |
Ok, heres the scoop. I have a 23mini with a soon to come stage 1 evt kit with stage 2 headwork. My rpms are already sky high (turning 4450ish with 10.25 inches left on my 11x10). Now, with these mods obviously brings up my rpms. I need to get them down. My dilemna comes with comprehending the world of props. Would I need to stick with the same 11x10 and just get more and more cup to bring it down or actually go with a larger diameter like a big blade? It seems the OOW rpms with the 11x10 would be sky high because of no extra weight and the cup wouldnt effect till it touches water. Yet the big blade would actually have more mass. Is this correct? Im just trying to figure out where I need to go with this. What size/route do yall recommend? Does an extra inch in cup have a standard ammount it usually drops the rpms? Just trying to find out some math here. I havent really dabbled in aftermarket, Ive only researched Mudbuddys stuff so if you have some other suggestions you think would fit, hit me. Thanks for help! |
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| Author: | craig [ Sun May 02, 2010 8:27 am ] |
| Post subject: | Re: Prop Padawan! |
Your best bet would be to buy a new prop and go from there. If your RPM's are still high with the new prop bring it to a prop shop and have them add a little pitch to it. 2 inches of pitch is about all you can add to a new stainless prop. 1 inch of pitch will bring your RPM's down 200-250 rpm. 2 inches would bring it down 400-500 rpm. You should try a big blade also. Maybe you can borrow one and see how it performs before buying one. |
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| Author: | th3 [ Sun May 02, 2010 9:18 am ] |
| Post subject: | Re: Prop Padawan! |
caleb/luke craig/ben |
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| Author: | duckman [ Sun May 02, 2010 9:25 am ] |
| Post subject: | Re: Prop Padawan! |
Before i would put any pitch in a new prop, why not get different gears, that would bring the RPM down also. That is what all the pros suggest |
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| Author: | craig [ Sun May 02, 2010 9:40 am ] |
| Post subject: | Re: Prop Padawan! |
| Author: | Caleb W. [ Sun May 02, 2010 11:19 am ] |
| Post subject: | Re: Prop Padawan! |
Getting a little better understanding now. However, would I need to stick with the standard diameter of 11 and just add pitch or go ahead and get a 12 or 12.25 and go from there? Dont want to end up with two brand new props. Any idea what kind of rpm drop I could see with the big blade? Also, If i just added pitch to the 11x10, with the mods, would it even be safe to rev up out of water? Seems like the OOW would still be sky high because of the same size, just more pitch. Yet the big blade would slow it down entirely. Is this correct? Thanks for the help. |
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| Author: | craig [ Sun May 02, 2010 12:02 pm ] |
| Post subject: | Re: Prop Padawan! |
| Author: | Caleb W. [ Sun May 02, 2010 3:30 pm ] |
| Post subject: | Re: Prop Padawan! |
Back when the prop was fresh 11x10 I was swingin 4300. However, I have a stage 1 coming with stage 2 heads. After the mods pitch will have to be added or more diameter will be needed. What Im trying to say is, out of water rpms will be the same at ANY pitch done on an 11x10 correct? Adding pitch is just tweaking the mass of the prop thats already there? The weight would be the same and the out of water rpms for this prop seems like it would remain the same (really high after the mods). The rpms shouldnt be afffected until that extra pitch hits resistance (water). However, if I went with a prop that actually had more mass (12-12.25 diameter), the OOW rpms would be brought down safely also. Its all up there in the head, just cant seem to get it into words. |
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| Author: | craig [ Sun May 02, 2010 3:48 pm ] |
| Post subject: | Re: Prop Padawan! |
Prop pitch & diameter have nothing to do with out of water rpm's dude. OOW rpm's will be the same regardless of which prop you use. |
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| Author: | Caleb W. [ Sun May 02, 2010 3:54 pm ] |
| Post subject: | Re: Prop Padawan! |
I gotcha I gotcha. For some reason when my OOW rpms went higher after my prop went down, I assumed more prop mass=less OOW rpms. So whichever route I go, adding more pitch, getting more diameter, the rpms after the mods will remain high? Im assuming gears would be needed to do this then (trying to stay away from that). |
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| Author: | craig [ Sun May 02, 2010 4:08 pm ] |
| Post subject: | Re: Prop Padawan! |
You will bring your rpm's down by either doing one of two things.....adding more pitch or adding more diameter. Either one will bring your rpms down. Gears are not needed although they can be used. How many people have you witnessed taking their Yamaha or Mercury outboard lower units off and having them re-geared to keep their engine at a certain rpm? If you buy a new prop and have 1 inch of pitch added to it.......it will be fine for the stage 1 mods. Your rpm's can easily be adjusted via the governor if they are too high. |
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| Author: | keestan31 [ Tue May 11, 2010 7:55 pm ] |
| Post subject: | Re: Prop Padawan! |
Not trying to start trouble but why are you so worried about your OOW rpms...do you run your motor wide open out of the water alot? |
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