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Hi all

I am in the process of rebuilding my jet pump as fitted to a Mercury 240efi. I am now stuck as I do not have the Pinion Gear Location Tool 91-831897. My pump housing has been powder coated (big mistake!) and I have fitted new bearings.

Now I presume that the shimming process for the pinion shaft assembly is to set the height so that the gears engage fully over the whole length of the teeth and not too high or too low. The shimming of the matching impeller shaft drive gear is to set the load on the gears?

Does anybody know of a tool that I can hire or buy at a good price? Looking on the net the cheapest is around US$150 excluding shipping to Australia. Is there perhaps another way of doing this?

I was thinking of firstly installing the impeller shaft, gear and bearing assy and then use a height gauge measuring from the pinion housing mount flange on the main jet drive housing down to a point on the impeller gear teeth. Then by measuring from the same point on the pinion shaft gear to the bottom of the pinion shaft housing the difference would be the required shims?

Any help would be greatly appreciated.
Purpose is to obtain proper mesh depth (contact pattern) of teeth. Is there some issue with the impeller shaft as well?

But you'll need more than just the pinion position tool, final step you need to confirm backlash using the backlash rod tool, dial indicator, etc.

How thick is the powdercoat, just subtract that from shim thickness. then measure backlash if you have the tools.

"NOTE: Average total amount of reading of indicator backlash specification is .007 inch (.18
mm) to .009 inch (.23 mm)."

Usually in our shop this job would be sent out, we let the drive guys do the gear shimming whenever it gets that far (chewed up gears, bearings, etc) otherwise we use the original shims for reassembly during a reseal.
Unfortunately... this it's the "Rear End" of a car. In that situation, you can mount the gears, and look at a physical patch for contact, and use a standard dial indicator to set lash. Personally... if you are digging that deep into the pump... then you need to buy the proper tools.

With that said... I'm cheap, and I would try.

1) I would make sure all the powdercoating is removed from the parts so they seat properly. (including bearing pockets)

2) Assemble the pump with the original shims, and a coating of yellow gear indicator.

3) Rotate the pump one revolution, and carefully remove the pinion, and inspect the patch.

4) Adjust the pinion shims to correct the patch.

5) Once set... check the lash, and adjust the shim on the impeller gear.

Basically, treat it like a car/truck axle.

I don't know how well it will work.... and you may wind up eating the gears... but it's a suggestion.

To me... the $150 for the tool is WAY cheaper than having to rip the pump out of the boat again, and replace the gears, and bearings when it fails.
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