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Posts: 427
Location: Roseau | I have a 16 foot with a 90 hp johnson. It came with 2 props aluminum- 14x17 and 13x19.
What type of top end difference would there be?
How about hole shot difference?
Right now it has the 13x19 on it, just wondering if I switch it out, the difference between the 2.
Thanks
Edited by Fisher 3/27/2007 8:24 AM
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Posts: 2384
Location: On the X that marks the mucky spot | The prop that runs your engine closest to it's red line at wide open throttle will be the one that has the best hole shot and top end. Each prop has it's own qualities and the variation from prop to prop in the same size and make varies as well. Proping a boat has a bit of black magic to it, sometime you just have to try it and find out for yourself.
That's probably not the answer you wanted, but it's the truth. Give them both a try, make sure you keep the rpm's in the recommended band and check your gps (not speedo). | |
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Posts: 3508
Location: Elk River, Minnesota | Well...treats had the first part correct, but the second part is not necessarily so.
The 14 x 17 has more blade surface area and a lower pitch, so it will definitely have a better hole shot, and pulling power. The 13 x 19 is higher pitch with a smaller diameter, which will be for speed on top.
My guess with both of these props the faster one will be the 13 x 19 hands down. The motor will have an easier time turning the 13 diameter prop since it is a full inch smaller than the 14 x 17.
Theoretically speaking here: Lets say your motor tops out at 5500 rpm with the 13 x 19 pitch prop. When you switch to the 14 x 17 two things basically happen..the larger diameter will cause the RPMs to go down (roughly 1/4"=100rpm), but the 17 pitch is 2 inches less which will increase your RPM (roughly 1" pitch=200 RPM). Both props would "theoretically" run at the same RPM by this, but the 14 x 17 will be slower...It will have the "umph" though that you would like for pulling skiers, tubes, boards, etc. The boat will be able to stay on plane a little easier due to the surface area of the props blades.
The 19 pitch will definitely be faster, but it will take a little more to get it "out of the hole" to some extent...but this is offset by diameter some too
I will agree that propping your engine to the Max RPM with a normal load. Then, you will have the power you need when you load up a little more.
All you can do is try the different props. Do a few test runs with each and see which you like better for your style of boating.
Steve
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Props