Aligning impeller shaft with midshaft housing

[Prem1x]

Yamaha gives a spec of 0.012" for impeller shaft runout, but I don't see anywhere a spec for how well the shaft should be centered within the hull where the mid-shaft bearing housing mounts to the inner hull. Anybody know how close to center this needs to be?

Background: the bottom of my ski was re-gelcoated and I think the extra thickness of the gelcoat where the jetpump mounts to the hull has thrown this off a little so I am planning on sanding it down some.

 

[sflsurfrider]

install the midshaft first. then, install the pump. its easier to do if the ski is upside down. bolt the pump where it sits (pushing fwd to seal the seal, of course). but make sure you shim ANY gaps between the pump and hull first.

 

[ski4]

wow, i just got in from doing this right now
pain in the a$$ since i had it all together but forgot to do this

so needless to say i had to do it backwards from this , but is all worked out and i got it to the point that i could just slide the housing onto the impeller shaft and all the bolt holes lined up perfectly

 

[D-Roc]

my hull had the shim thickness written on it from the factory for the pump, of course if you painted your ski if may be gone.

 

[ski4]

mine had 1.0 written by the aft inserts
would that be 1 mm? 1 shim?

 

[D-Roc]

yes i believe so.

 

[ski4]

hmmmmm, i think i ended up building it up a bit more than 1 mm but it seems awfully good to me as it sits, i'l leave it

 

[Prem1x]

I forgot to post a pic of the thru-hull.

 

[T-bone]

it looks like from the picture you filled in the alinement pin holes.

 

[Freestyleriverrat]

I do pretty much what you are doing. Install the pump (make sure the drive shaft is not bent though) and adjust it to be right in the center of the bulkhead where the midshaft assembly mounts. You can check to make sure the driveshaft is straight by spinning it once it is in position. If it oscelates you may have a problem that will give you some vibration you can't fix through shims :frown: Once that is in I like to bolt the midshaft assembly up, then install the motor and shim that, then shim the midshaft if necessary.