RE: Having problems setting the throttle on my seamaster
Yes, you can adjust the travel of the servo for over 100% of it initial set up. The extra travel is insurance for the safety of the gears of the servo, so it is recommendable to stay around 100% of its range of operation.
If you note that you have to go over in a good amount, then think on go back to the throttle linkage and start over.
Good Luck.