Measuring impeller setback

[Jcary85]

Sorry if this has been covered (tried searching), but how does one measure impeller setback? Can I use a straight edge on the back of the impeller and measure to where the threaded part starts?
I have an impeller which was not in the correct box when sold to me (I think) and want to verify everything.

 

[Harbor]

@speedysprocket he did my prop cut back and may know... The rear cone on my prop appeared to need to be cut back an equal amount or it would hit the stator veins, so iam not thinking measuring down from a straight edge will work.

Edit: now that I think about it, both needed cutting but a different amount, I think mine was 5mm off the center threaded hub and 3mm off the cone

 

[speedysprocket]

So many different castings, it’s hard to know where it started and how to measure and tell what was taken off. It’s a relative thing, though. They can say it’s cut to whatever, but what matters is how it fits the pump.

 

[Idallgo]

Measuring impeller setback is crucial for getting your setup.

 

[IsaacMoore]

You're on the right track - using a straight edge on the back of the impeller and measuring to where the threaded part starts is a common method. This measurement helps ensure that the impeller is positioned correctly for optimal performance and clearance.

 

[Storbeck]

I'm curious what use is the number? I've always ignored the number and just shimmed (or machined) to make it fit how I want.

 

[Jcary85]

I'm curious what use is the number? I've always ignored the number and just shimmed (or machined) to make it fit how I want.

Ya since 5 years ago when I asked this I came to the same conclusion. What matters is how close the trailing edge is to the stator veins.

 

[Storbeck]

Ya since 5 years ago when I asked this I came to the same conclusion. What matters is how close the trailing edge is to the stator veins.

Lol ah yeah see it now.

 

[IsaacMoore]

You're on the right track - using a straight edge on the back of the impeller and measuring to where the threaded part starts is a common method. This measurement helps ensure that the impeller is positioned correctly for optimal performance and clearance.

If you're unsure about the impeller's specifications or if it was not in the correct box when sold to you, verifying everything is a smart move. Double-checking measurements can save you from potential issues down the road. Using a virtual real size ruler can be a handy tool for this task, as it allows for accurate measurements without the need for physical tools.

 

[IsaacMoore]

You're on the right track - using a straight edge on the back of the impeller and measuring to where the threaded part starts is a common method. This measurement helps ensure that the impeller is positioned correctly for optimal performance and clearance.

If you're unsure about the impeller's specifications or if it was not in the correct box when sold to you, verifying everything is a smart move. Double-checking measurements can save you from potential issues down the road. Using a virtual real size ruler can be a handy tool for this task, as it allows for accurate measurements without the need for physical tools.

 

[TheBuzzard]

It's usually engraved on the inner hub what the pitch and cutback is but takes 2 seconds to spin the prop on and make sure it clears. I've found wrist pin washers in there for shimming purposes . Not sure the trailing edge needs to be right next to the stator veins. That makes for a smaller prop needed. More gap means more slippage and bigger prop. Zero clearance means one pebble thru there means it gets chewed

 

[Brett Roman]

Hi, very nice meet you. Would like buy setback guage. 148 krash pump need tune.

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