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| Prop https://www.smwebhead.com/phpBB3/viewtopic.php?f=2&t=9790 |
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| Author: | jdclay [ Tue Jul 10, 2012 2:17 pm ] |
| Post subject: | Prop |
Not many lakes around my area nor people that know what they're talking about when it comes to boating. I had a 21 pitch prop but my hole shot wasn't where I wanted it. I was told to go down in pitch so the guy stated that 17 pitch is what I needed. Now, hole shot is better but I lost 12 mph on top end AND it's running rpm's really high for the speed I'm going. 30 mph is bringing 4500 rpm which is not even close. Most of you know way more than the people I've talked to so suggestions are welcome!! |
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| Author: | RotaryRacer [ Tue Jul 10, 2012 2:26 pm ] |
| Post subject: | Re: Prop |
What boat, engine and outdrive? What were your RPMs and top speed with the 21 pitch prop? |
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| Author: | Mark T [ Tue Jul 10, 2012 2:32 pm ] |
| Post subject: | Re: Prop |
I have a 14.5 x 19 prop. run 4700 rpm and will do mid to upper 40 MPH depending on waves. |
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| Author: | jdclay [ Tue Jul 10, 2012 2:33 pm ] |
| Post subject: | Re: Prop |
1996 195 sundowner, 302 ford, volvo penta. Top speed was 46 with 4 adults in boat and rpm's were around 4500 with 21 pitch. Two people in boat and I was going 30 with rpm's running 4500 with 17 pitch. |
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| Author: | RotaryRacer [ Tue Jul 10, 2012 2:49 pm ] |
| Post subject: | Re: Prop |
With the 21 in pitch you are already running close to the max RPMs for the motor. Is the motor FI or carb'd? I'm pretty sure the max for the FI motor is 4600 rpm. Regardless, you won't want to go down in pitch much or you run the risk of overrevving the motor. Do you know the manufacturer/model of the 21p prop? You will gain approximately 200 rpm for each inch of pitch you go down...so a 20p prop will bring up up to 4700 rpm. You may have to look at different blade geometry and number of blades to get the performance you are looking at. A cupped prop with 4 blades will give better hole shot than than a 3 blade non cupped prop. Unfotunately, prop selection is often a trial and error process. |
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| Author: | jdclay [ Tue Jul 10, 2012 2:54 pm ] |
| Post subject: | Re: Prop |
That's what I'm finding out. So, What I need is a 4 blade 20 pitch stainless correct? Or that's the best route to go as of now? |
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| Author: | RotaryRacer [ Tue Jul 10, 2012 3:03 pm ] |
| Post subject: | Re: Prop |
jdclay wrote: That's what I'm finding out. So, What I need is a 4 blade 20 pitch stainless correct? Or that's the best route to go as of now? That seems like a reasonable and pretty good approach. Although, you didn't mention Al vs SS previously. Is the 21p you have now SS? What about the 17p? If the 21p is SS, then yes your idea to go to a 20p 4-blade SS is probably pretty good. If it is Al then you may actually be able to stay with a 21p and go SS, 4 blade cupped. |
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| Author: | jdclay [ Tue Jul 10, 2012 3:10 pm ] |
| Post subject: | Re: Prop |
both are Al. So stay 21p and 4 blade cupped? Also, I'm in West Texas and this guy is telling me to go to lower pitch due to elevation purposes. Thoughts on that?? |
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| Author: | ric [ Tue Jul 10, 2012 3:15 pm ] |
| Post subject: | Re: Prop |
That came with a 14.25 x 21 pitch from the dealer. I hate 4 blade props they offer no advantage over 15mph what so ever over a good 3 blade stainless in any lake test results, they're a waste of money IMHO unless you're a boat towing service. I've done hours of reading articles, basically the two best props on the market are the volvo penta 3 blade stainless and michigan wheel ballistic. Personally I would go with 14.X19.... and the Michigan Wheel Ballistic 14.5x19, but the VP 14.75x19 has a tad more blade area for out of the hole but might get 1-2mph slower then the MW. Both should still keep you in the mid upper 40's. So if you're after more bottom end and don't mind 45mph, just go with the best all around prop on the market... VP SS. If you can, find a VP dealer in your area they should have a test prop u can take home and try. |
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| Author: | jdclay [ Tue Jul 10, 2012 3:37 pm ] |
| Post subject: | Re: Prop |
No VP dealers around here but I'll def be looking for that prop on the net. Thanks for the help fellas. I'll now walk in to both dealers in town and have more info than both of those jack wagons.... |
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| Author: | BartsPlace [ Wed Jul 11, 2012 3:41 pm ] |
| Post subject: | Re: Prop |
At the risk of muddying the water, changing prop geometry, blade count, and material should only be done when you are certain everything else in the drive chain (including the engine itself) is operating as designed. Many people mistakenly look to the prop first. Prop changes can vary between subtle and not-so-subtle. Unless you have the completely wrong prop for your engine/boat/elevation, a prop change is rarely a dramatic performance increase. That said, there are a few new-ish prop shaping techniques that have produced some nice results. Most of the major players are employing these now. As mentioned by ric, Volvo and Michigan are solid options. I would add Solas on the conservative side of the scale with Stiletto and Turbo on the aggressive end. The Stiletto Advantage SS prop I bought for my Baja rocked my world over the standard Mercury BlackMax aluminum prop. Find a good prop shop (they'll have access to most of these). Then try them out until you find what you like. Good luck! |
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| Author: | jdclay [ Thu Jul 12, 2012 10:32 am ] |
| Post subject: | Re: Prop |
Thanks for that. I have the standard AL prop as well and I've check everything else. I put my old prop back on and it managed way better than new prop. I was going 30 at 3200 rpm which is pretty spot on (having an 1/2 inch chip in one of my blades). I'll do some searching and get my problem fixed. Thanks for the input! |
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| Author: | jvthundercat [ Fri Jul 20, 2012 6:06 am ] |
| Post subject: | Re: Prop |
Stilletto. Not much more to say on it really. |
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| Author: | DaleG [ Fri Jul 27, 2012 3:13 pm ] |
| Post subject: | Re: Prop |
Aluminum props can be easily repaired -- and aluminum props can also be repitched - - if you think 20 is they way to go -- just have your repaired and repitched -- |
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