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Name: |
Chevy4x4
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Subject: |
Buying a new prop - Need Help
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Date:
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5/22/2005 1:46:58 PM
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Help would be great from anyone who might know a bit more than me.
I have a '96 Baja Outlaw with a 350mag, Bravo 1 Outdrive. I'm currently running a Rapture 21 pitch 3 blade prop. The boat will run 54 mph (gps) at 5200 rpm's. I'd really like to push it up to 60 mph and i'm not sure what type of prop I should run. Should I go up to a 26 pitch 4 blade? I don't mind loosing holeshot as I will still have the rapture prop for skiing ect. Any ideas for top end? Thank for your time!
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Name: |
MotorMan
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Subject: |
Buying a new prop - Need Help
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Date:
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5/30/2005 4:04:26 PM
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First try trimming up the out drive until you hit your max rpm. I have a 23" 3 blade you can try. It is for a Mercucy V-6 o/b, but I think they interchange. It is a "ventilated" prop. That means it allows some exhust gas to ventilate out causinng the prop to "slip" at low speed. The rpm's go up at low speed, allowing the engine to gain rpm into the power band. You get a better hole shot. The ventilating stops as boat speed increases. If you have a 21" and you are only hitting 5200 rpm, the 26" you mention will only bog down the engine. Avoid 4 blade props. More wetted area means more friction loses. They are for pulling skiers.
You may already have more prop than you need. Ideally, You should hit max rpm with the correct prop. But if that is 5500, there is not much left. You are unlikly to hit 60mph with just a prop change. A very clean bottom is a must. rule of thumb: A boat that can hit 60 needs twice the hp to hit 80.. ken@alabamabass.com What is the red line on this engine? Ken
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Name: |
Chevy4x4
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Subject: |
Buying a new prop - Need Help
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Date:
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5/30/2005 11:07:05 PM
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I think i'll purchase a 14.25x23 3 blade and give this a shot. The previous owner tried to sell me his extra prop that he claimed would push the boat about 62. The price was high, and sadly I can't remember what type of prop that was. I've done a good bit more research into the situation and I agree that 26 pitch is way to much. Thanks for the advice. I'll let you know how it turns out.
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Name: |
MotorMan
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Subject: |
Buying a new prop - Need Help
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Date:
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5/30/2005 11:53:00 PM
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Be very very careful with that prop. I think it will over rev your engine. example: My 85hp Evinrude came with a 13 1/4 x 17" prop. It was a good all around 15.5' tri-hull prop. The 13"x 19" I got produced no more speed. The 13 3/4x15" however was a good "stump puller" I used to pull up salom skiers. It was hard on the engine and ran up the rpms with no skier.
Perhaps you can try some props out at a good prop shop. One perfect prop from a prop shop is better than trying out by buying a new one. A prop builder can make a speed prop perfect for the boat/motor combo. They can build a 22 3/4 " pitch if that is what your engine needs to reach its proper band of rpm
That is why I have this ss 23" prop. It did not help my 175 Merc o/b and I am stuck with it. good luck.
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Name: |
Osms
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Subject: |
Buying a new prop - Need Help
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Date:
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5/31/2005 10:43:07 AM
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Pretty much enough's been said--except: To get best prerformance, load your boat the way your use it - gas, people, coolers, junk, etc. and run WOT. Check the max rpm you get against the max recommended rpm range. Manufacturers will quote a range like 4200-4800--stay close to the upper end for best performance, life of engine, mileage, etc. In this example, if you are turning 4600 rpm with your current prop you need to decrease your prop pitch by 2" to get up to 4800 for best results. And vice versa.
Unfortunately, a prop can not add what the engine cannot deliver. Horsepower rules. By the way, Prop shops can change the pitch of your existing aluminum or stainless prop plus or minus 2". These lake dealers probably will tell you differently--because they only sell props.
Mobile, AL has a number of prop shops. Cost should not exceed $100-150 to re-pitch.
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Name: |
MotorMan
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Subject: |
Buying a new prop - Need Help
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Date:
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5/31/2005 1:08:29 PM
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Hi again, I think I put the statement I made about the 23" prop being a high rev prop backwards. I was looking at the 17" part. Now a 17" pitch prop would be a very high rpm prop: for a race engine only. If you are concidering a new prop, do what Oms said: go to a prop shop. My 23" prop bogged down my 19' Carlson boat with 175 Merc. It would go no more than the 19" did which was 60mph with low gas, little wife driving and a tail wind.(not kidding) With a full tank of gas, 4 people, cooler, ice, adult bevs (what the hey, beer), into a 15 knot breeze, and a bottom that had been in the water for 10 days, it would only go 53mph. I am going to guess that if you want to hit 5600-6000 rpm, and go a little faster, the prop will be 20 1/2" pitch by your same diameter. The shop may just do a little "cupping" and maybe a cut to make it more of a "chopper blade".
I believe that there is no "Horsepower Fairy". Your seller may have embelished to you about hitting 62 mph. If the boat did it, it had his kid on throttle like my wife, low on everything.
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Name: |
Chevy4x4
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Subject: |
Buying a new prop - Need Help
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Date:
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5/31/2005 1:57:40 PM
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Thanks for the information, I hadn't even considered a prop shop.
Anyone know of one around the lake, or North of the lake. I live in BIrmingham.. so any where in between I can do.
Thanks again, you have been most helpful.
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Name: |
Osms
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Subject: |
Buying a new prop - Need Help
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Date:
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6/1/2005 11:17:04 AM
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Locals will have to send it off. Most prop shops will be on the coast where most of the work on bigger props is. Can't make a living on lake boats. Try the Yellow Pages on the internet for the Mobile area-- You may have to ship it down there.
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Name: |
GoneFishin
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Subject: |
Buying a new prop - Need Help
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Date:
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6/4/2005 2:11:48 PM
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here is a response from another site
dont lug that engine going to a higher pitch will cut your upper rpms.
lugging the engine with too much pitch is tough on
the engine. you should prop your boat to
run close to the max rpms when lightly loaded. I've
done that, ruined a powerhead, (trying to squeeze out
a few more miles per hour) and wont do it again.
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Name: |
LifeTime Laker
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Subject: |
Lake Martin Prop Shop
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Date:
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6/6/2005 9:16:03 AM
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Lake Martin Prop shop on Dadeville road in Alex city. Cant remember his phone number and it is listed wrong in the phone book. I got the number off the wall at Niffers. His last name is Martin, cant remember his first name. Great guy and will help in any way he can.
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Name: |
ShoeFly
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Subject: |
Buying a new prop - Need Help
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Date:
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6/7/2005 11:22:20 AM
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Hey Chevy, Nice to see other Baja owners!!!!! I have a 23 Mirage that you are welcome to try and if it works for you then we will go from there.
-ShoeFly 30 Outlaw
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Name: |
SCARAB MAN
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Subject: |
Lake Martin Prop Shop
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Date:
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9/14/2005 4:06:34 PM
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Farley Stewart in opelika does all my prop work.I always cup my props on the ends to give more bite but thats outboards,I have a scarab 29 ft and twin 350 carbs.I only turn 4500 rpm with a 23" prop.
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