Impeller to pump clearance for mag pump?

[Philip Clemmons]

What should it be?

Mine seems way too tight!

 

[Matt_E]

I had a similar problem when a new 140 mag impeller was ordered from Skat.
The hub had been machined back too far by Skat. This resulted in the hub hitting the pump.
An extra shim was necessary.

 

[Philip Clemmons]

This is not a hub issue, but actual blade diameter or liner diameter......................

There is around .0035 to .004" clearance. Just the little bit of torque from tightening the pump causes it bind against the liner. This is with no nozzle or midshaft-nothing is hitting anywhere except the feet of the wear ring to the hull. If I leave them loose it spins freely, but tightening them up distorts the ring enough that it rubs. I though most oem "new" specs were around .008-.012. I know the mag is likely set up tighter for performance, but there has to be some room for bearing runout, etc..................

Experimenting with shims on the feet now to see if that helps.; Looks like the hull is not 100% flat where the feet go.................................

 

[#ZERO]

If you shim the pump assembly so the drive shaft is perfectly centered with the mid shaft housing hole in the hull, that clearance should be acceptable.

 

[Philip Clemmons]

Check pms................#zero

 

[CarterB]

not to mess up your post but whats too much clearance for a stocker setup. im at .016

 

[Matt_E]

This is not a hub issue, but actual blade diameter or liner diameter......................

There is around .0035 to .004" clearance. Just the little bit of torque from tightening the pump causes it bind against the liner. This is with no nozzle or midshaft-nothing is hitting anywhere except the feet of the wear ring to the hull. If I leave them loose it spins freely, but tightening them up distorts the ring enough that it rubs. I though most oem "new" specs were around .008-.012. I know the mag is likely set up tighter for performance, but there has to be some room for bearing runout, etc..................

Experimenting with shims on the feet now to see if that helps.; Looks like the hull is not 100% flat where the feet go.................................

If it spins fine before you tighten the pump, then the problem is improper shimming.
That's actually the quick & dirty way to align a new mag pump Art @ Jetworks told me.
Bolt it in and see if it binds.

Bolt only the two front bolts in (wear ring) and see how far the rear two are off.
Shim appropriately, and bolt down. Should be good to go after that.