Engine Alignment Kits Not Accurate


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I'm posting in this forum because it is most read by the 2-stroke junkies. :D

After my battle with the Seadoo Twin Engine Speedster engine alignments.... which were "spot on" when I got done modifying the engine bases, I encountered issues with the engines being difficult to rotate after installing the Jet Pumps. Further checks have shown me something very profound. The alignment kit I use draws tight to the pump mount surface (the entrance of the pump flange.) That's all well and good if that surface is perfection matched to the pump mount bolt surfaces. That isn't the case on these two pump mounts. The surface where the 4 pump mount bolts make up tight is the true alignment surface. If anyone has encountered shims under the jet pump bolts that is likely the reason for the shims. If mount bolt surfaces are not parallel and can throw the alignment off a good bit and cause problems with engine rotation.

I'm a machinist by trade and rotating equipment I've done most of my career. First check you do is loosen mount bolts one at a time to determine what we call "soft foot" and sure enough when I loosened specific mount bolts the engine turned free. Funny thing the driveshaft was easy to slide back and forth in the PTO. I will likely modify 140mm and 155mm jet pumps for a more accurate alignment processes in the future. Just thought I'd share. Here I am thinking the alignments I do are perfect and probably in a lot of cases they are "spot on" but this incident has shown we can't take it for granted. From now on I'll straight edge and a feeler gauge to measure across the pump mount areas. Touchdowns everyone !!
I doubt this level of perfection is necessary but I am trying to resolve problem or at least determine what it isn't. One thing for sure it is all parallel now so I've done what I can. I removed the thru bolts and machined the landings to the correct height to match the pump mount surface. The variance along the mount was (.032") or 1/32" so now I can't get a (.005") feeler gauge between the strait edge and the mount surface so it's good. First time I had a problem like this. That's all I'm gonna do for sure.