'72 Mercury 402 Gearbox issues

[Niallator]

Hi, looking for help with my Merc 402. I've taken over a job on a motor that someone else had taken apart. I'm changing the water pump. All seems to be well with the motor however I cannot get the lower end (gear housing) back in place. I've read similar posts here but still haven't been able to figure out my problem. I'm pretty sure it's engaged in forward gear and I can mount the lower end most of the way until contact is made somewhere inside the gear housing that pushes the gear selector shaft back up towards the carb. It feels as the splines on the selector shaft aren't sitting home properly, I've tried mounting it while moving the throttle to and fro but no joy. To make things even more difficult I'm fresh to these motors and don't have a full understanding of some of the parts and how they operate, and lack a good enough quality diagram. Any help would be appreciated.

 

[mthieme]

Re: '72 Mercury 402 Gearbox issues

Sometimes you just gotta jiggle, wiggle and shake.
They can be stubborn especially with new seals (if you did the full kit).
Did you grease the splines?

 

[Laddies]

Re: '72 Mercury 402 Gearbox issues

Some of the mid size engine the shift shaft does not stay centered in the torque tube when the lower unit is remove , so when installing the unit you have to hold the shaft with wire or needlenose pliers just below the swivel tube while reinstalling the unit

 

[Niallator]

Re: '72 Mercury 402 Gearbox issues

Thanks for the advice! I've now been told that the lower unit may be faulty. Is it true that the gear selector shaft should not stay put in the lower unit once removed?

 

[Laddies]

Re: '72 Mercury 402 Gearbox issues

No thats not the truth, if it worked before it should work now, the shift cam may be worn a little so the unit don't stay in forward as well as a new one and make it difficult to renstall the unit. Thats exactly why we always put them together in rev instead of fwd as the manuals says.