TOPIC: to make go into right gear-71 merc 500 -50 hp

i installed a new impeller on my mercury 500 50 hp.stupid me turned the small shaft with splines that puts it in forward,neutral and reverse.now it goes forward all the time.how can i get it into the right position?
Thanks

Welcome to the lower unit / waterpump club.

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Same mistakes are made over and over.

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Take the lower unit off again.

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put lower unit in nuetral and control in nuetral and re-assemble

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Or some prefer lower unit in forward and control in forward.

but how do i know what position is forward or neutral or reverse just by turning the shaft.........thanks

When the propshaft clicks when turned clockwise it is in forward gear. If it turns and locks both ways, that is reverse. Put the lower unit and engine shift into reverse, then install the lower unit. Should work then.

The shift shaft sticking up out of the lower unit has about 1/3rd of its rotation that turns freely or without resistance both clockwise and counter-clockwise.
This 1/3rd of a circular motion is all Forward gear and as mentioned, the propshaft should make a clicking noise as you rotate it clockwise (when looking at it from the prop-nut end),...And the propshaft should not turn counter-clockwise without the driveshaft beginning to turn and you DO NOT want to allow the driveshaft to turn counter-clockwise because it could most likely force the impeller blades to flip the wrong way and they may not return to their correct position again resulting in poor impeller performance.
Now,...Turn the shiftshaft counter-clockwise (when looking down at the top end of it) until you meet resistance. Continue counter-clockwise against the resistance until the shiftshaft 'clicks' into a notch you can feel.
Release your grip (probably with pliers) and the shiftshaft should stay put. The propshaft should rotate either direction smoothly and quietly. This is Neutral.
Continue turning the shiftshaft counter-clockwise to the next 'click' or notch felt and you are in Reverse.
In Reverse the propshaft will not turn either direction without forcing it to turn the driveshaft too.
Attempting to put the lower unit onto the motor in Reverse gear is a bit risky IMHO, because the least little unscheduled bump during assembly and the shift shaft will jump counter-clockwise off the reverse cam (in the lower unit) and if assembly is completed in this position and you attempt to shift back to Neutral,...Something is gonna break if any force is applied.
The lower unit will need to be removed and the shift shaft re-positioned to either Neutral or,..Forward as per the manual.
If I have a controller and shift cable that were already adjusted and attached to the motor before the lower unit was removed, I prefer Neutral for assembly.
Actually,...Any more I normally use Neutral in all cases, but the Manual suggests Forward gear.
Thom

thank you sir for your expert suggestions.....you know how us dumbrednecks are!

thanks for your help sir!

Dr.......i did exactly as you said and it worked perfectly.I appreciate your help sir....i owe you a steak dinner!
take care
Fluke