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| RPM & Propeller Pitch https://www.smwebhead.com/phpBB3/viewtopic.php?f=11&t=6083 |
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| Author: | cwwright2002 [ Wed Jul 07, 2010 6:08 pm ] |
| Post subject: | RPM & Propeller Pitch |
Had a great time on Saturday, with the "new" sundowner, but hit a dead head or something and chewed my new aluminum prop to pieces. also, only getting around 3300 top end rpm, and not all seems right, had a 14 1/2 x 19 propeller on it. I am reading that WOT is between 4200-4600, but she is SLOW!!! Looking to increase speed, perhaps maintain a higher RPM... Does anyone know what the stock prop size on the four winns 1992 225 sundowner with 5.7 L 351 OMC engine? If I can zero back out the prop size perhaps I can get the RPMS up. Also, after about 3 hours run time, started to get power fluctuations, eventually cut out, found a dropped plug wire off the port rear cylinder, would this explain my intermittent power issue? She idled okay into harbor but would cut in and out when demanding more than 2000 rpm. Neighbor suggested I replace plugs and wires, but was thinking if I fix the prop and or reduce pitch I could get higher rpm. Would a missing plug wire impact RPM that much as well? |
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| Author: | Jim_R [ Wed Jul 07, 2010 7:05 pm ] |
| Post subject: | Re: RPM & Propeller Pitch |
You'll want to bookmark this site: http://www.fourwinns.net/fastfacts/fastfact/1992/225Sffp24-25.pdf My read is the stock prop is an aluminum 15 x 17 prop that should get you 44 - 47 MPH. Only the 454 engine was setup stock with a 14.5 x19, but that was rated at 47 - 50 MPH. |
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| Author: | The Kid [ Thu Jul 08, 2010 8:36 am ] |
| Post subject: | Re: RPM & Propeller Pitch |
Yes running on 7 cylinders instead of all 8 you are going to have performance problems. If the boat can't plane out you will never get the rpms and top speed. You could also have a hub that is slipping in the prop if its an older prop. But since its trashed I would start with a new 15x17 and fix the wire situation and go from there. |
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| Author: | Walt [ Thu Jul 08, 2010 9:53 am ] |
| Post subject: | Re: RPM & Propeller Pitch |
Get the tune-up first... Plugs, wires, fuel filter at a minimum. After the engine is running right, then try the prop you have and plug the numbers into a prop-slip calc. Make sure you use a GPS for the speedo first! http://www.go-fast.com/Prop_Slip_Calculator.htm |
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| Author: | cwwright2002 [ Thu Jul 08, 2010 10:40 pm ] |
| Post subject: | Re: RPM & Propeller Pitch |
Thanks guys for the advice. I am purchasing a 15x17 as a second, will try both to see maximum performance. I think I am going with the tune up this weekend, then take it out to see how it does!!! |
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| Author: | cwwright2002 [ Thu Jul 08, 2010 10:42 pm ] |
| Post subject: | Re: RPM & Propeller Pitch |
I should mention that I had the 14x19 repaired as well, it will likely be relegated as a spare, no sense in throwing it out since it was cheap to fix the chewed up portions... |
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