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Prop/Jack Plate Adjustment?

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EvinrudeIntruder175

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Solved my fuel/oil issue finally! Now for some fine tuning! I have a 1991 Ranger 481V powered by a 1991 Evinrude Intruder Spitfire 175hp. Prop is a stainless 4-blade cupped tip OMC Shooter 27pp. According to the specs on my motor the optimal rpm range should be between 4800 and 5500. I am barely making 4700 rpm at WOP and just over 55mph on GPS. This boat with this motor setup should be pushing over 60mph. It has a Pow'r Drive jack plate by Springfield. When running WOP, my water pressure is approx 23psi. I have never adjusted one before and have no knowledge of specific prop usages. My holeshot is good, top end is my issue. Should I start with trying new props? Or raise Jack Plate some first?
 
Is your motor adjusted so that the cavitation plate is one inch below the bottom of the boat? That is supposed to be the optimum adjustment. Others will chime in with more info and experience than I have. Good luck
 
I'm not sure yet. Will find out this evening. I'm trying to contact a few dealers in my area and talk about trying a few different props also. Just wasn't sure if I should get the motor set perfect first, or the proper prop? I'm guessing set the jack plate first. Then find the best prop. I am willing to give up a little holeshot for the right top end. I want to be able to outrun some of the local guys that always beat me to the back end of the lake.
 
With a jackplate you have a certain amount of setback because of it. The more setback you have the higher the motor needs to be. There are charts or formulas to determine this. Ask around the prop section of this forum, I imagine you'll get some good info there.
 
Never set the anti cav plate 1" below the boat!! You'll be dragging it through the water, and that's not the idea. At the deepest, it should be level with or above the keel. With a jackplate, you can set the engine higher, depending on how much set back the plate has. I run a 200 XP Evinrude on an 18' Charger SK hull (pad 'V' hull) and I get 80 mph at 6,000 rpm. I have a 5" setback on the plate, and I run the motor with the anti cav plate about 8" to 10" above the keel. 3 Blade 28" pitch SS prop, cupped for bow lift. And no, I don't have a low water pickup mounted, just the top 2 holes filled in on each side of the water intakes.
 
EvinrudeIntruder175 said:
Solved my fuel/oil issue finally! Now for some fine tuning! I have a 1991 Ranger 481V powered by a 1991 Evinrude Intruder Spitfire 175hp. Prop is a stainless 4-blade cupped tip OMC Shooter 27pp. According to the specs on my motor the optimal rpm range should be between 4800 and 5500. I am barely making 4700 rpm at WOP and just over 55mph on GPS. This boat with this motor setup should be pushing over 60mph. It has a Pow'r Drive jack plate by Springfield. When running WOP, my water pressure is approx 23psi. I have never adjusted one before and have no knowledge of specific prop usages. My holeshot is good, top end is my issue. Should I start with trying new props? Or raise Jack Plate some first?
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A 4 bladed prop will increase hole shot over a 3 bladed prop but you will lose on the top end. Only way around that is to decrease the pitch. From factory your motor should have between 14.75x19 pitch 3 blade prop and 14x25 pitch 3 blade prop. Your running a 27 pitch 4 blade prop. You kind of went in the wrong direction with a 4 blade. When you increase drag (add another blade) you decrease pitch. The only way to correct your issue is to get a new prop. I f you still want a 4 blade prop I recommend one with a pitch below 22. That added blade will act like a 3 blade with a 25 pitch. Now if you want a SS prop, you'll need to decrease pitch again. The added wait of SS vs aluminum is enough to drop a couple hundred rpms. It's personal preference really, but crucial to get pitch right. Hope this helps.
 
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