# Impeller Shimming



## JMR (Mar 2, 2011)

I know Outboard Jets says to shim the impeller when the liner gap wears to more than 1/32"... but Outboard Jets also says not to shim too closely...but how much is _too_ close? Is the goal of shimming the impeller to try and *maintain* a 1/32" (.0312) liner gap and not any tighter than 1/32"? 
1/32 seems like a wide gap size to me...
Thanks in advance for experience on this.


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## Lil' Blue Rude (Mar 2, 2011)

They recommend that you keep it at 1/32". The biggest thing is don't get it too close because it will groove the liner if you do.


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## fatherfire89 (Mar 3, 2011)

When I added shims I would keep adding them until I could hear the impeller touch the liner when I turned the drive shaft. Then I removed a shim, turned the shaft again to make sure there wasn't any rubbing, and called it good. If your impeller is just touching, the removal of a 1/16" shim will leave a 1/32" gap between liner and impeller ( 1/16" X sin(30), assuming ~30 degree angle between drive shaft and liner walls) I am no expert but I haven't found anything wrong with this method.


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## mercury jet (Mar 20, 2011)

fatherfire89 said:


> When I added shims I would keep adding them until I could hear the impeller touch the liner when I turned the drive shaft. Then I removed a shim, turned the shaft again to make sure there wasn't any rubbing, and called it good. If your impeller is just touching, the removal of a 1/16" shim will leave a 1/32" gap between liner and impeller ( 1/16" X sin(30), assuming ~30 degree angle between drive shaft and liner walls) I am no expert but I haven't found anything wrong with this method.


 
I to have used this method, and it also works for me to


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