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Posts: 425
Location: Roseau | I am currently running a 13x19 aluminum on a 90 hp two stroke johnson and at wide open throttle am getting about 5650 to 5700, the max should be 5500. I am wondering if I go to a 21 how many RPMs will it drop? With 3 guys and some gear it takes just a bit to get on plane, do you think the hole shot will be affected very much?
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Posts: 5874
| Going from a 19 to a 21 will affect your hole shot. If you have trouble getting on plane now, it will be worse. You might want to try a 19 SS prop. It sounds like you are getting some blade flex with your aluminum prop, and this will not happen with a SS prop. |
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Posts: 357
Location: Long Prairie, Minnesota | Going up in pitch will drop your RPM's of your boat. I believe anywhere from 200-400 rpm's. It will also affect your hole shot, but should do so in a positive manner. With more pitch to your prop, it will "bite" more of the water and thus should pop you out of the hole and up on plane faster. Do you know what the max rpm's for you motor is? I know for my 90hp Optimax it is 5700 rpms. Knowing that will make it much easier to determin how far down in rpms you need to go. |
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Posts: 433
Location: Cedarburg, Wisconsin | If you stay at 19 pitch and go to a cupped SS it will most likely cut the RPM's by around 200 and if you get a SS with vent holes your hole shot should be about the same. The only way to tell for sure though is to actually run the prop and see what happens.
With my Johnson 150HP there was about 300 rpm's less when I went from an AL to a SS and no doubt it was the blades on the AL flexing and slipping more. A SS prop is just a little more efficient grabbing water because of the cup on the blades. As I was below the RPM's I needed for max, I actually ran faster with the AL because of the extra RPM's pushing a heavy fishing load, but when I lightened the load the SS caught up with the AL prop and even passed it up for top end. So you can see, load means a lot. |
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Posts: 14
Location: Olathe< Kansas | Getting the right peop for your boat / load / motor is a trial and error.
Hopefully you can find a prop shop or dealer that will let you try a few different ones.
I would try a 4 blade SS prop 18 or 19 pitch. With 3 guys and a full tank of gas-- the 4 blade will help you hole shot.
Good luck.
Rick
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