I recently bought a second hand boat which seems to be well looked after by the previous owner. But the throttle control is harder than usual when shifting into neutral from both forward an reverse positions. Otherwise, the stiffness of the control seems ok.
Does anyone have an idea of what could be the problem?

 

Welcome to the forums.

Is it a tiller or a remote controll system?

The first thing that comes to mind would be a stiff shift cable. Is there any sharp bends in it, or a kink from tilting the motor?

 

It is a remote control system. Visually, the cables look ok. No kinks or sharp bends and they seemed lubricated at the motors' end. I am thinking in disconnecting the cables at the motors end to have a look whats going on. Any tips or suggestions?

 

That's the first thing I would do. I think that year the cable is just cliped in place so it's easy to remove. The cable should be easy and smooth to shift. At that time you can shift the gearcase with the cable off. Make sure it's not running but you may have to spin the prop by hand so the gears mesh in the gearcase.