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Tcondra

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I have tried researching this but can't find an answer. I have a 16 foot pontoon that I bought new last year. It came with a 25 hp motor with a 9 pitch prop. The boat will only go 8 mph. I want more speed than that. I am of course not looking to pull skiers or enter a race lol. Dry weight of boat w/o motor is 1250. Motor 5000 t0 6000 rpm. Any advice would be appreciated. Thanks
 
We need to adjust the prop size to the sweet spot in the max RPM range. With your average load, does it seem to be taching up, or is it lugging? Since we don't have a tachometer, we have to go by ear. A 9" pitch for a 25 might be considered a power prop, so I would say it could already be taching up pretty high. If it is reaching 6000 RPM, maybe we can go to a 3 blade 10.5 by 11 pitch. So the 10.5" is the circle diameter of the prop and the pitch means "how far the prop will push itself, (with no outside forces considered), in 1 complete revolution.
 
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timguy said:
We need to adjust the prop size to the sweet spot in the max RPM range. With your average load, does it seem to be taching up, or is it lugging? Since we don't have a tachometer, we have to go by ear. A 9" pitch for a 25 might be considered a power prop, so I would say it could already be taching up pretty high. If it is reaching 6000 RPM, maybe we can go to a 3 blade 10.5 by 11 pitch. So the 10.5" is the circle diameter of the prop and the pitch means "how far the prop will push itself, (with no outside forces considered), in 1 complete revolution.
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It seems to tach up to around 5300 to 5500. Motor doesn't feel like it is lugging.
 
You did not mention what sort of motor you have. Is this an MFS25C ? If your tachometer shows about 5400, you need less pitch. If this is a normal 3-blade prop, you need at least 2 inches less pitch. Perhaps a 4-blade HT prop would help. You want to get as close to 6000 as possible.
 
pvanv said:
You did not mention what sort of motor you have. Is this an MFS25C ? If your tachometer shows about 5400, you need less pitch. If this is a normal 3-blade prop, you need at least 2 inches less pitch. Perhaps a 4-blade HT prop would help. You want to get as close to 6000 as possible.
Click to expand...

Yes that is my motor. I had it figured wrong. I thought I had to go to a higher pitch for more speed. Do they make a lower than 9? What is a HT prop?
 
You can only go to more pitch if the motor has the POWER to turn that higher pitch prop.-----Lots of tutoring is available from various propeller company websites.
 
Tcondra said:
Yes that is my motor. I had it figured wrong. I thought I had to go to a higher pitch for more speed. Do they make a lower than 9? What is a HT prop?
Click to expand...

If you need to add 600 RPM, you need about 2" less pitch. Stock on the 2-stroke is 11 for the long model. The 4-stroke did not come with a stock size; the dealer selected one for the motor.
Props from 8 to 14 pitch; also some in stainless. HT is High Thrust, with 4 blades.
https://tohatsu.com/accessories/prop.html
 
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