Home › Forum › Ask A Member › 1975 Mercury 650 lower unit assembly › Re: 1975 Mercury 650 lower unit assembly
Just because you put the original shims back in does not mean it is properly shimmed. Every set of gears is slightly different. Also, is is possible you have the shims on the upper driveshaft mis-matched? There are sometimes shims UNDER the support bearing, as well as ABOVE the bearing. This is so the water pump base above the bearing seats against it. If you put all those shims on one side or the other, it may make a difference in pinion gear height. If the gear is too low, you may get the issue you noted.
How is the gear lash between the pinion and forward gear? I don’t have the book here, but it should be no more than a few thousandths. The gears should NOT be jammed together with no clearance.