Help needed with Mariner 75hp gear shifting issue

[Crazy1]

My First Post

I'm very new to boating. My motor is a 75 Mariner, about 2000 model.
Recently It became increasingly difficult to engage the forward and reverse gear - now its just impossible.
I have removed the linkages inside the top, and I am unable to move the shifter / selector by hand.
Where could I start looking for the cause? Does the shift rod in the pics look OK? Should the shaft run in the center?

Regards,
Jakes

 

[faztbullet]

Remove the lower unit as problem is more likely with it internally...

 

[Crazy1]

Thanks

Anything tricky I should watch out for? I'm not new to mechanical stuff, but I've never worked on an outboard before.

 

[faztbullet]

Just watch for coupler that may fall loose ,looks like aluminum thimbal with splines inside...