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Discussion Starter · #1 ·
I bought a Michigan Rapture SS Prop today for 95 bucks off of craigslist its 14.25 diameter x 17 pitch, Lookin forward to try it out on the boat. Thought I made out pretty good today.

P.S. he was also selling a Stiletto I believe 15x19 for $110 but that was a little too much pitch for my use
 

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You will know once you try it. I ran a Stiletto on my old boat w/5.0 Cobra. It worked pretty good on that particular boat and it was a nice looking prop.
 

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Instead of buying someone else's prop to see if it works, why not go to a real prop shop, get some advice and try a couple props first before you make your final decision!

Did you do any math before you set out to find this prop at a low price or is this just a shot in the dark for you?
 

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BoinkSwag000 said:
I bought a Michigan Rapture SS Prop today for 95 bucks off of craigslist its 14.25 diameter x 17 pitch, Lookin forward to try it out on the boat. Thought I made out pretty good today.

P.S. he was also selling a Stiletto I believe 15x19 for $110 but that was a little too much pitch for my use
Not knowing yourboat, power, outdrive and ratio it's a little hard to give any advice. And what are you running now and with what results.

ghart has the right idea. Shops will let try a prop (used one) to get an idea where you want to be and then they will sell you a new prop
 

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Re: Re: Michigan Rapture SS

enticer said:
Not knowing yourboat, power, outdrive and ratio it's a little hard to give any advice. And what are you running now and with what results.

ghart has the right idea. Shops will let try a prop (used one) to get an idea where you want to be and then they will sell you a new prop
In the end for less money that buying a bunch of props you have no idea how they will work. Go to the pro and let them help you.

Their price will be money well spent. :p:
 

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Discussion Starter · #7 ·
I have an 89' 233 Wellcraft Eclipse with the mercrusier
5.7 liter 260hp and alpha 1 outdrive, I have been using a 14.5 x 17 aluminum prop for cruising which allows the motor a max rpm of 4400 right in its reccomended rpm range of 4200-4600. With that prop I get about 31 mph at 3400 rpm which is what i cruise at.


The prop I bought is 14.25 x 17, so I'm thinking the motor will hit a higher max rpm overall and not quite sure how it will affect mph, I'm thinking maybe pick up a mile or two.

..... Sorry for not posting any specs earlier, I know better then that !!!!
 

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You may see a very slight increase in RPM, other than that I suspect you'll get the same results.

The new prop being stainless will give a tad better performance only because of the "flex factor" being eliminated.
 

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Not really sure what the factor is, just that stainless is stiffer!
 

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Discussion Starter · #11 ·
I know that diameter and pitch influence performace and that is a balance between the two, I know that pitch is the measure forward distance over one roatation. but how does diameter directly influennce the performance of a prop.
 

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The way it was explained to me, the diameter of a prop is like the diameter of a wheel. The greater the diameter, effectively, the higher the ratio.
 

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ghart said:
The way it was explained to me, the diameter of a prop is like the diameter of a wheel. The greater the diameter, effectively, the higher the ratio.
I think you mean the pitch of the prop. Change of pitch is effectively similar to changing gear ratio in a vehicle.
 

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RSCHAP1 said:
I think you mean the pitch of the prop. Change of pitch is effectively similar to changing gear ratio in a vehicle.
I was talking only about diameter, the prop being discussed in this thread only had a diameter change, the pitch was the same on both props discussed.

You are correct comparing pitch to vehicle gear ratio, but wheel diameter affects performance as well.

Look at it this way, the pitch is the same as the tooth count in a differential. The more teeth on the ring gear as opposed to the pinion gives a low gear ratio, lots of power at the cost of top speed, like having a 19 pitch prop for example.

Conversely, fewer teeth on the ring gear, as opposed to the pinion, gives less power but higher speed, as in having a 23 pitch prop, in this example.

The diameter of the prop is the same as putting 14 inch wheels on a vehicle, shorter circumference, more pulling power at the cost of top speed, lets say like a 14 1/2 inch prop.

Conversely, replacing those hypothetical 14 inch with 16 inch wheel which has a longer circumference will reduce pulling power but give a higher top speed, as in a 15 1/2 inch prop in this example.

Somebody correct me if I'm wrong. :blush:
 
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