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Engine prop help

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Jmeyer73

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I have a 2000 90hp Johnson 2 stroke with a 1996 115 Johnson lower unit it runs great. Im running approximately 35 mph WOT at 4100 RPMs. I wanted to know what prop I could use to get more speed. The prop I have now is a Stiletto ( 2319 01319)
 
Way off, sir. That's a 19" pitch. In other words one revolution will move the prop/boat, 19". Too aggressive for 90 hp on your rig. I would study some prop tables, but you need to gain 1000 + rpm. Might be looking at a down size from that 13 1/4 diameter, as well as stepping into a 15" pitch. With each inch of pitch drop you will add 200 to 250 rpm, however.....this is not really a straight line graph. As rpm increases, so does horsepower and torque. So.....as you adjust pitch downward, and rpm increases, less pitch adjustment will allow a greater percentage of RPM, horsepower, and torque response. Sorry if I made this confusing, but to put it simply, there is no real definitive way to calculate props....gotta get close, load your boat, go for a boogie cruise, and check for correct RPM. Your 90 should run in lower 5000's at full bore.
 
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timguy said:
Way off, sir. That's a 19" pitch. With each inch of pitch drop you will add 200 to 250 rpm, however.....this is not really a straight line graphYour 90 should run in lower 5000's at full bore.
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Good info Tim.

Jmeyer, what kind of boat is this running on? Assuming your engine is in top shape and running properly you're looking at going down to a 15P or even 13P prop to get your engine in an acceptable RPM range. A 15P would potentially bring you up to 4,900RPM and a 13P could jump to 5,300 RPM. Check out the Prop Selection guide on this site to give yourself a good place to start searching: http://www.marineengine.com/parts/solas-propeller/

There is also a page that lists all props available for your 90HP: http://www.marineengine.com/parts/s...1995-2007&model=V4+Large+Gearcase+(15-Spline)

Also, make sure exactly which lower unit you have on the motor. There were options for 13-spine and 15-spline prop shafts, so make sure you have that right before ordering any props.

KJ
 
kevinj said:
Good info Tim.

Jmeyer, what kind of boat is this running on? Assuming your engine is in top shape and running properly you're looking at going down to a 15P or even 13P prop to get your engine in an acceptable RPM range. A 15P would potentially bring you up to 4,900RPM and a 13P could jump to 5,300 RPM. Check out the Prop Selection guide on this site to give yourself a good place to start searching: http://www.marineengine.com/parts/solas-propeller/

There is also a page that lists all props available for your 90HP: http://www.marineengine.com/parts/s...1995-2007&model=V4+Large+Gearcase+(15-Spline)

Also, make sure exactly which lower unit you have on the motor. There were options for 13-spine and 15-spline prop shafts, so make sure you have that right before ordering any props.

KJ
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A 2000 17’ predator center Console 24C7A858-6A58-4966-A8B2-B69DC0052EA3.jpeg
 
kevinj said:
Good info Tim.

Jmeyer, what kind of boat is this running on? Assuming your engine is in top shape and running properly you're looking at going down to a 15P or even 13P prop to get your engine in an acceptable RPM range. A 15P would potentially bring you up to 4,900RPM and a 13P could jump to 5,300 RPM. Check out the Prop Selection guide on this site to give yourself a good place to start searching: http://www.marineengine.com/parts/solas-propeller/

There is also a page that lists all props available for your 90HP: http://www.marineengine.com/parts/s...1995-2007&model=V4+Large+Gearcase+(15-Spline)

Also, make sure exactly which lower unit you have on the motor. There were options for 13-spine and 15-spline prop shafts, so make sure you have that right before ordering any props.

KJ
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13 spline ok so now i know the prop I have on the boat now is a 13 19 pitch
a friend gave me a 13 1/4 X 17 aluminum prop same spline. How much difference will this one make ? I want more speed
 
Well the only thing running your motor to 6000 rpm on the muffs will accomplish is showing you the inside of the motor when parts come flying out. What is your compression? Do you have spark on all cylinders? You may want to determine the health of your motor. That motor should be turning 5500 rpm, if you want to go faster get a bigger motor.
 
flyingscott said:
Well the only thing running your motor to 6000 rpm on the muffs will accomplish is showing you the inside of the motor when parts come flying out. What is your compression? Do you have spark on all cylinders? You may want to determine the health of your motor. That motor should be turning 5500 rpm, if you want to go faster get a bigger motor.
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compression is 128-131-132-135, motor has spark on every cylinder has new power pack, new coils, new plugs , new wires, new sensor under timing cover, new timing cover.
 
Something is wrong here.-----The boat should fly with that motor and the 19" pitch.----The 115 HP gearcase has the same gear ratio as a 90 HP .----Best have the motor run on a dyno to determine actual power output.-----Perhaps tachometer is wrong.----Find a shop to help you !!----Do not wind it up to 6000 RPM in neutral as that proves nothing here.-------I say the motor is running on 3 of 4 cylinders !!----Why all those new parts ????
 
racerone said:
Something is wrong here.-----The boat should fly with that motor and the 19" pitch.----The 115 HP gearcase has the same gear ratio as a 90 HP .----Best have the motor run on a dyno to determine actual power output.-----Perhaps tachometer is wrong.----Find a shop to help you !!----Do not wind it up to 6000 RPM in neutral as that proves nothing here.-------I say the motor is running on 3 of 4 cylinders !!----Why all those new parts ????
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It was in gear on the muffs and i just hit for a second couple times. I just kept changing parts when I couldn’t figure out why it wouldn’t go over 2100 rpms, come to find out the power pack and one of the coils were bad. Ordered new cdi coils and one of them were bad. Its firing on all cylinders now Im thinking carburetors may need to be adjusted also gonna take it out Saturday with a 13 1/4 X 17 prop and see what it does.
 
Really-----In gear on the trailer is still neutral.------The prop does no work !!----That test means nothing and can damage the motor.--------Post a picture of the rear of the boat when it is floating in the water.
 
Racer, what do you mean by the above statement ?? If you have the boat backed in far enough you can load the motor.
 
Racer is probably sleeping now.....like I should be too. I took him to mean the boat being on the trailer.....hooked up to a garden hose.......doesn't matter which gear it's in, prop only pushing air, so same as neutral.......no load, good way to mess up your motor.
 
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