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Jupiter Fl sandbar 75mph pass

boatman4021 said:
Hey Jupiter, What prop are you running now? 3 or 4 blade? boatman
Click to expand...

When I first put the 8" setback bracket on two weeks ago it was 60 degrees out. We hit 77 mph on the Livorsi Speedometer turning a Trophy Plus 26 four blade at about 4600-4700 rpm....made three passes before it became too dark to play. The video was shot in 80 degree weather, turning 4500-4600 rpm at 75 mph...I didn't really get trimmed out till after the boat passes the camera...I may try my Tempest 25 again..maybe the extra setback will help control that Tempest from chine walking.
 
boatman4021 said:
Did you mean 5500 to 5600rpm's? boatman
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Boatman, I went behind my Livorsi tach and set it to the 12 pole position. My tach used to read 6900 rpm at wot. Now the passes I've made read anywhere from 4500 to 4700 rpm. I checked the propslip calculator and the math equates to roughly 73 mph which is pretty close to the Livorsi speedometer. If you take the 26 pitch prop and add 1 for being a cupped performance prop, plug in the 1.62 gear ratio, plug in 4600 rpm and hit calculate you will see the 73mph speed. I'm still scratching my head on this one...it seems that I should be able to turn the motor to 5500 rpm....
 
With 1.62's I need around 6000rpm to break the 80mph mark with a 26P Trophy Plus. Something is wrong there.

No offense, but why not just get a GPS and be done with it.
 
hotdaddy27 said:
With 1.62's I need around 6000rpm to break the 80mph mark with a 26P Trophy Plus. Something is wrong there.

No offense, but why not just get a GPS and be done with it.
Click to expand...

Hey Hot Daddy, before I added the setback I ran with my Garmin handheld GPS, Full tank, two adults at 73 MPH....but the tach was setup incorrectly and showing 6900 rpm...
 
Jupiter, My 2100 with 225efi, 1.75 gears ran 74@ 5500 with a 27" Trophy+. You may still have a tach problem. What about the 1.62 gears? Where did they come from? 4500rpm's with 1.62's is 69.9mph before slip, -10%= around 63mph. boatman
 
boatman4021 said:
Jupiter, My 2100 with 225efi, 1.75 gears ran 74@ 5500 with a 27" Trophy+. You may still have a tach problem. What about the 1.62 gears? Where did they come from? 4500rpm's with 1.62's is 69.9mph before slip, -10%= around 63mph. boatman
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Using 1.62 ration, 27 pitch, 4600 rpm = 73 mph or the calculator from Bam Marine. They are experts in the field of go fast boats. It's just an average..boat weight, bottom design, etc. also come into play.
 
The formula that I use gives max mechanical speed possible for a given rpm, gear ratio, and prop size. No way can anyone run faster then the mechanical speed. Boat size and weight and set up will only take away from the mechanical speed. Not trying to be an a$$ or a know it all, but 4600 with a 26" and 1.62's will never see 73. It iss impossible. boatman:cheers:
 
Jupiter

I punched in those numbers on Bam's site. It does give a theoretical speed of 73. That speed would not include slip etc. In a best case scenario I've seen for a Pulsare is 6-7% slip calculation. This is a very ideal situation backed with accurrate tach and GPS numbers. If you drop in 6% slip it comes up with an actual speed of 69.

http://www.go-fast.com/Prop_Slip_Calculator.htm

I still think something is a miss with your tach. 4600 is way low. I would think you'd want to turn that motor to upper 5K. or if you do have 1.62's I'd drop down in prop to reach that rpm goal.

Good Luck
 
hotbeek said:
Jupiter

I punched in those numbers on Bam's site. It does give a theoretical speed of 73. That speed would not include slip etc. In a best case scenario I've seen for a Pulsare is 6-7% slip calculation. This is a very ideal situation backed with accurrate tach and GPS numbers. If you drop in 6% slip it comes up with an actual speed of 69.

http://www.go-fast.com/Prop_Slip_Calculator.htm

I still think something is a miss with your tach. 4600 is way low. I would think you'd want to turn that motor to upper 5K. or if you do have 1.62's I'd drop down in prop to reach that rpm goal.

Good Luck
Click to expand...

I'm going to hopefully run the boat again (by myself) on wednesday with my GPS and check my tach..maybe my eyesite is getting old and it said 5600 rpm instead of 4600 rpm??? Maybe I have 1.75 gears???...I just assumed the 1.62 gear ratio was standard. It may make more sense because if I input into the prop slip speed calculator 1.75 ration/26+1=27 pitch/5600rpm=82 mph theoretical speed X 8% slip = 75 MPH which is what the Livorsi speedometer shows....
 
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