figuring out impeller pitch...

[Roo]

i have a couple impellers sitting here, skat trak stampings, no pitch stampings like some Solas props i have had in the past...

is there a way to figure out the pitch of the prop without buying a Watcon tool? take some measurements at some key spots, etc?

-Andrew

 

[SUPERTUNE]

Andrew, If they were made by Skat-Trak, mostly they would have numbers engraved in the inside of the inner hub with an electric engraver.

 

[ATS_Aaron]

I was able to use our magnetic base angle finder that we use for fabrication. Also I think Greenhulk has a PDF file that you can download and have Staples or whoever print on clear paper. Then wrap it and tape it.

Aaron

 

[Watcon]

Pitch gauge

http://www.watcon.com/Catalog_Pages/Impeller_Pitch.htm

 

[Matt_E]

Andrew, If they were made by Skat-Trak, mostly they would have numbers engraved in the inside of the inner hub with an electric engraver.

In my limited experience with Skat-Trak impellers, those numbers have good potential to be wrong. I wouldn't take Skat's word for what the pitch is.

 

[kevbo]

Its easy to plot the exact pitch of any impeller with a scale and a $10 scientific calculator. Mark the outside of the blades every 1/2 inch from leading to trailing edge. Set the impeller on a flat surface and measure the height of each mark. Use trigonometry to convert the distance and height into degrees. Most modern impellers are almost flat at the leading edge with pitch increasing until about halfway down the blade where it becomes constant. The last number on the prop is usually the same as the last two inches of the blade. This gives the best indication of the props load. The first number never makes any sense. I have found that the leading edge angle has most to do with cavitation vibration. Freestyle boats need a flat leading edge for best hookup and smooth running at low speeds. Skis usually go a little faster with a steeper leading edge but vibrate out of the hole. There are only a couple of props that are perfect out of the box, most need to be hammered on for best results.

 

[egbrig]

Just get the WATCON guage. There will be no guess work. Nothing could be simpler.

 

[upstand2]

Menards,Hoime depot, $5 pitch guage.

 

[upstand2]

A protracter will even be fairly accurate.

 

[egbrig]

I find it funny that people always want info, then when good info is given someone else has to jump in to make themself sound as if they know something. ROO, you want to measure the pitch of an impellor. Go ahead and spend $5.oo on protractor and see what a pain in the a$$ it is to use. Such a sugjestion is made by those who haven't done it. Spend the money and get the right tool for the job and you'll be so much happier. With the WATCON guage you'll be able to see the rate at which the pitch changes not just the beginning and ending pitches. This is just as important as everything else but once again some expert just sent you down the pain in the a$$ trail.

 

[Cross]

I find it funny that people always want info, then when good info is given someone else has to jump in to make themself sound as if they know something. ROO, you want to measure the pitch of an impellor. Go ahead and spend $5.oo on protractor and see what a pain in the a$$ it is to use. Such a sugjestion is made by those who haven't done it. Spend the money and get the right tool for the job and you'll be so much happier. With the WATCON guage you'll be able to see the rate at which the pitch changes not just the beginning and ending pitches. This is just as important as everything else but once again some expert just sent you down the pain in the a$$ trail.

I couldnt agree more. Spend a little $$$ and really see what pitch is doing. I have used this tool to measure a lot of props, and you would be surprised at what differences the three blades can have (even ones that had been "tuned").

 

[Flash-FX]

That's a good idea to check the pitch. I thought that after you spend big loot from Skat-Trak it's a done deal, unless your pump ingests debris. I just took a look at those "pitch/degree" rings over at Watcon's site.....Hmmm which one is for the 144mm impeller?

140-142mm

Is there one in between not listed like 142-146mm?

146-148mm

155-158mm

 

[snowxr]

I have a Watcon guage for 144 props. They fit perfect. I just called Randy and asked for one.

 

[Foximus]

not to mention your usually talking about different angles at the root of the impeller and at the face of the blade.