Impeller Shimming

[JMR]

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.

 

[Lil' Blue Rude]

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.

 

[fatherfire89]

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.

 

[mercury jet]

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