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| New prop makes slow to gain rpms http://www.mudmotortalk.com/mmt_v2/viewtopic.php?f=41&t=2572 |
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| Author: | willett [ Mon Jun 15, 2009 4:59 pm ] |
| Post subject: | New prop makes slow to gain rpms |
I got a new prop not even sure the pitch and cup but had been running a 12x13 modified stock prop...now runnin this new modified stock prop It killed my hole shot and was slow getting up on plane and even with only two people could only run right around 4150 rpms unless trimmed way high then was a pain to control and could barely break 29 mph Also right on take off the motor would kinda wanna bog and cough Think its a mixture of carb adjustment and too much pitch or cup in the prop? Or what could it be? |
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| Author: | deadbird8 [ Mon Jun 15, 2009 8:56 pm ] |
| Post subject: | Re: New prop makes slow to gain rpms |
Too much cup is like a brake on the motor. Pitch should take you down about 200RPM per inch added. Have them change one thing at a time. |
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| Author: | Brinkleydog [ Thu Jun 18, 2009 10:32 am ] |
| Post subject: | Re: New prop makes slow to gain rpms |
Put it in the mudd for about 30min and you will gain your speed back up......LOL When we ran at Caddo and SnaggyChirp  said my rig never seen 30+ I had that brand new prop with heavy tip and struggled to get 27 mph. Now after puttn 4-5 hrs on it im back up to over 30 with a mod. load. After i get my boat and ProDrag runn machine i will be able to get 30 with and not have to run WFO.Good luck with that new prop and build. Later JA |
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| Author: | RC [ Thu Jun 18, 2009 11:48 am ] |
| Post subject: | Re: New prop makes slow to gain rpms |
Too much tip curl killed my takeoff rpm transition and top end speed more than anything else. I always had a prop going back and forth in the UPS system! Once I somewhat figured out what did what, the best prop was one that I took a dewalt grinder and file too it. Had one built to duplicate it, and kept it as the spare. At one point, I had a stock prop that would steadily run over 38mph, so they are capable of running ok. Adding pitch didn't really do much at all. There is some weird science by the last couple inches of the tips. Hard part is finding the middle ground here and there, that works all around. End game prop did everything pretty damn good, and hardly threw any kind of a rooster tail......pretty dang efficient! |
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| Author: | Brinkleydog [ Thu Jun 18, 2009 11:59 am ] |
| Post subject: | Re: New prop makes slow to gain rpms |
Nice info there RC. I can see the resaon behind no tail with an effecient prop. I noticed that the stock prop had a much greater tail than my 12x14 hopkins. never put my mind to why it was that way, but I can see why after your post. |
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| Author: | craig [ Thu Jun 18, 2009 1:41 pm ] |
| Post subject: | Re: New prop makes slow to gain rpms |
I would take off 1 inch of pitch. That should put your rpms around 4350-4400, |
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