The motor (15hp) has so much torque it will either throw off weed or light plastic immediately, or break the nylon shear bolts.
This is a really lame suggestion, but as it is all a bit new to you, is it possible you turned off the switch beside the toggle switch in the heat of the moment?
The good news is the more that you practice the easier it will become, you will quickly be able to wander through a marina in 25kts+ of winds stern too, without a thought.
Happy new year.
Seafever of Cuan
SM 425 Redline 2004