Final Verdict : to shim pump or not to shim??

[IDoSeaDoo]

Hey all. I bought a ski once, and the pump had shims between the pump body and the hull. Judging from the discoloration on the hull, I figured these to be OEM shims. This made sense to me, as the through-hull fitting isn't necessarily perfectly aligned with the way the pump bolts up. This was confirmed with my alignment tool (legit tool, not a home-made job). When I would put the alignment shaft in, it would NOT center with the thru-hull fitting. I figured this would unevenly wear the carbon seal, so I shimmed the pump body to the point where when I stick the tool in, it's more/less centered with the fitting (I used a mirror to see all around it). Using a new neoprene seal, I experienced no cavitation with the shimmed pump, but as I switched to a traditional carrier seal,I can't attest to the carbon seal wearing well or not.

Anyway, I know there are those of you here that say to NOT shim the pump body. What is the final verdict? To shim or not to shim? I ask as I may be doing this for others in the future and want to be professional about it.

Thanks!

 

[68ragtop]

I have had one ski that had shims on the pump & they really made a difference. I tried to align it without the shims & I just couldn't get the engine squared up to the drive shaft without adding what I felt was too many engine mount shims. I shimmed the pump & it took very little to get it aligned perfectly afterwards.

My take is, I think it really depends on the ski. It would seem there are instances where the pump mounting surface is just a fuzz off from the motor mounts. Given the length of the driveshafts, a slight adjustment at the pump can greatly reduce engine shims. So in a nut shell, I feel like pump shims are a good choice when engine shims become too abundant to get it aligned.

I could be wrong here, this is just my experience & nothing more.

 

[IDoSeaDoo]

Thanks ragtop, that's the kind of input I'm looking for. I take it you didn't have cavitation or leaking as once mentioned to me?

 

[68ragtop]

I had no issues, however I did use a neoprene seal on that one.

 

[Minnetonka4me]

Yup the neo seal is important if it takes alot of shimming on the pump. I have rarely needed much on jetskis, but almost always need them on the boats.

You can usually tell it will need pump shimming when no matter what you do, when the pole will only go about half way into the PTO w/o binding...which means the pole is coming in at an angle. that, or your shimming is so off the engine is sitting at an angle.

Also it is important on 580-720s to try to center the motor on the bed plate. I had one twisted that was a total bitch, then we shoved it to one side and it again made it tough. So the 3rd time we just tried our best to center it, and boy did that one align up quick.

Last tip for the 580-720s...when you start stacking shims, it limits the side to side adjustment of the motor. Again, if you shim the bottom of the pump in that situation, it will drop the angle of the tool and give you more adjustment of the motor by the need for less shims.