trolling motor problems

run a 12 volt 50 lb all terrain tm... i have a breaker on it that use to trip all the time... last year i took out the plug and just hardwired the tm wire to my wire to the battery... my last few trip's it's been so windy i have had to run it on five speed... well after running it for 7 to 10 second's continuously on five it short's out and just get's hurky jerkey? it never has tripped the circuit breaker and the wire's back by the battery don't get hot? i can run it continuously on 4 with no problem but 5 is when it act's up. checked my connection's and wiring and everything seem's to look fine... any suggestion's? thank's all!

Probably the armature gets hot and opens up when it draws too much current. Look at your brushes and armature connection.