Lower unit gear shift spline location

uncledoug01

Cadet
Joined
Oct 18, 2011
Messages
6
I have a mercury 1985 115hp tower of power. I have rebuilt the water pump and having trouble getting the gear shift spline lined up correctly. There is not a detent to locate natural. Are there any procedure to perform this task?
Thanks
 

hotrod53

Chief Petty Officer
Joined
Oct 16, 2009
Messages
508
Re: Lower unit gear shift spline location

Did you remove the stepped gear from the shaft in the process as I did without first marking it? That thing can go back on as many ways as there are splines. Others will chime in, but what you need to do is put the L/U in reverse by turning the shift shaft with pliers or vice grips, reinstall the stepped gear so that the ramp is at its highest when in reverse and lined up with the reverse lock rod, that is what locks your motor down to the frame in reverse. You put your controller in reverse, and you slip it all back together.

I mention the step gear because you can actually get it all together and have the gears all work but if the reverse lock gear is not installed right, your motor will climb out of the water in reverse. That gear causes the reverse lock rod to rise and therefore turns the clamp that grabs the bar on the motor bracket.

I have been exposed to all of this but I had help, that's why I say hopefully others will chime in. There is a way to confirm if you're in reverse by turning the prop... some ways it clicks, some way it drives, ect. Thru the process, just be sure not to turn your driveshaft or flywheel counterclockwise or you risk turning your impeller inside out.
 

uncledoug01

Cadet
Joined
Oct 18, 2011
Messages
6
Re: Lower unit gear shift spline location

Did you remove the stepped gear from the shaft in the process as I did without first marking it? That thing can go back on as many ways as there are splines. Others will chime in, but what you need to do is put the L/U in reverse by turning the shift shaft with pliers or vice grips, reinstall the stepped gear so that the ramp is at its highest when in reverse and lined up with the reverse lock rod, that is what locks your motor down to the frame in reverse. You put your controller in reverse, and you slip it all back together.

I mention the step gear because you can actually get it all together and have the gears all work but if the reverse lock gear is not installed right, your motor will climb out of the water in reverse. That gear causes the reverse lock rod to rise and therefore turns the clamp that grabs the bar on the motor bracket.

I have been exposed to all of this but I had help, that's why I say hopefully others will chime in. There is a way to confirm if you're in reverse by turning the prop... some ways it clicks, some way it drives, ect. Thru the process, just be sure not to turn your driveshaft or flywheel counterclockwise or you risk turning your impeller inside out.

The shaft from the motor down to the foot was not removed. When I removed the foot I turned the splined gear shifter on the foot to see if the gears engaged. The unit will go in forward but I can't seem to find reverse. I was able to find neutral but no reverse and the shaft seems to turn further than the cable will move it. As far as I know the motor was shifting ok before I removed the foot.
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,558
Re: Lower unit gear shift spline location

Turn the shift shaft CCW looking down on it. You will need a cresent wrench to gently coax it back to neutral. It should lock in on the detent. Set the Mercontrol to neutral and reinstall gearcase.
 

uncledoug01

Cadet
Joined
Oct 18, 2011
Messages
6
Re: Lower unit gear shift spline location

I will try to install foot when I get the water pump rebuild kit.
Thanks for the help
 

schematic

Lieutenant Junior Grade
Joined
Jan 12, 2008
Messages
1,102
Re: Lower unit gear shift spline location

ditto chris1956. also rotate prop shaft back and forth when trying to find shift positions by turning shift shaft.
 

uncledoug01

Cadet
Joined
Oct 18, 2011
Messages
6
Re: Lower unit gear shift spline location

Thanks for the help guys. The motor is up and running. I now have water coming from around the lower spark plug. Looks like it is coming from the gasket for the water jack cover. Can I replace the gasket without removing the block from the unit.
Thanks
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,558
Re: Lower unit gear shift spline location

You can, however, those 1/4-20 bolts like to break when you go to remove them. Putting some silicone caulk on the source of the leak usually works.
 
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