Changing the pulley size 3.3 and 20hp.

Overly Cleaning Service

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Travis Overly
I purchased a used no name truck mount earlier this year. 20hp kohler, cat pump, 3.3 blower.

It does fine but after looking around it appears 20hp is a bit much for a 3.3 blower. I looked at the pulley sizes this morning. They are both 8 inches in diameter. Does that mean when I am turning the motor at 3000rpms I am turning the blower at 3000rpms as well? Does this sound normal?
I would like to quiet the unit down a little and maybe save some fuel by lowering the engine rpm possibly.
Couldn't I under drive the blower?
 

Todd the Cleaner

Todd Cottino
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I have a similar setup. I had a 20 hp I actually just replaced it with a 24 hp and a 33 blower. I set the pulley ratios so that the engine runs at 2500 and the blower is running at 3600.

If I were you I would definitely change your pulley and speed up the blower for sure. You will see a huge increase in vacuum with a 600 rpm increase on the blower.

I also changed out my blower silencer which made a huge difference in the amount of noise.
 

Overly Cleaning Service

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Oct 22, 2014
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I have a similar setup. I had a 20 hp I actually just replaced it with a 24 hp and a 33 blower. I set the pulley ratios so that the engine runs at 2500 and the blower is running at 3600.

If I were you I would definitely change your pulley and speed up the blower for sure. You will see a huge increase in vacuum with a 600 rpm increase on the blower.

I also changed out my blower silencer which made a huge difference in the amount of noise.


Do you remember what size pulleys you were running? Where did you get replacement pulleys from?
I have a muffler for my blower silencer. I am considering a glass pack after it to dampen noise more. I think the loudest part is running this old 1998 Kohler at a high rpm though.
 

Todd the Cleaner

Todd Cottino
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Do you remember what size pulleys you were running? Where did you get replacement pulleys from?
I have a muffler for my blower silencer. I am considering a glass pack after it to dampen noise more. I think the loudest part is running this old 1998 Kohler at a high rpm though.
I don't remember my exact sizes however here is a pulley ratio calculator you can use. http://www.culvermotor.com/Engineering-Formulas/Pulley-and-RPM-Calculator.html

I put your info in, if you leave the drive pulley at 8 inches you would want to put a 6.67 (so 6.5) inch pulley on the blower to have the engine running 3000 rpm's and the blower 3600.

I got my pulleys from a local shop called Aztec Bearing. Try finding a local shop to you that sells pulleys. One of the larger national chains is Bearing Belt & Chain. If you have a hard time finding a supplier you can go to your local auto parts store and ask where the best place is to buy pulleys.
 

comfort carpet care

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I don't remember my exact sizes however here is a pulley ratio calculator you can use. http://www.culvermotor.com/Engineering-Formulas/Pulley-and-RPM-Calculator.html

I put your info in, if you leave the drive pulley at 8 inches you would want to put a 6.67 (so 6.5) inch pulley on the blower to have the engine running 3000 rpm's and the blower 3600.

I got my pulleys from a local shop called Aztec Bearing. Try finding a local shop to you that sells pulleys. One of the larger national chains is Bearing Belt & Chain. If you have a hard time finding a supplier you can go to your local auto parts store and ask where the best place is to buy pulleys.
Todd that calculator is great, thx for the share!
 
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Average Guy CCer

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Jun 8, 2015
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I purchased a used no name truck mount earlier this year. 20hp kohler, cat pump, 3.3 blower.

It does fine but after looking around it appears 20hp is a bit much for a 3.3 blower. I looked at the pulley sizes this morning. They are both 8 inches in diameter. Does that mean when I am turning the motor at 3000rpms I am turning the blower at 3000rpms as well? Does this sound normal?
I would like to quiet the unit down a little and maybe save some fuel by lowering the engine rpm possibly.
Couldn't I under drive the blower?
Yes and it's easy will save fuel and wear on the motor