My father in law has a scooter from merit and it does not go very fast anymore. he said he has charged batteries and changed fuse but still doesnt go as fast as it uses to.

Shell Could be a couple of things but I would suspect the throttle pot. If the scooter is 4-5 years old or older the motor brushes might need replacing. If dad has the scooter outside and it gets damp the brake assembly might be sticking also If it gets rusty. If Medicare paid for dad's scooter I would contact a repair service to check it out and repair it since Medicare will pay for 80% of the repair cost. You can call Repair Express @ 1-877-581-3733 to see if they have a tech in your area or contact the provider that sold your dad the scooter to see if they have a repair service Hope this helps