with no load. Sometimes a failing winding will allow the motor to run fine but when you load it up some part of the winding will open due to heating and cause the motor to stop. Yours sounds like the motor is working but working to hard. Any pinch point in the circuit will cause heating. By that I mean a high resistance will cause a voltage drop. Or, a voltage drop will cause a high resistance. Each case is heat and that heat will show up somewhere in the circuit in some form. Their is an old saying that "you don't want to let the smoke out of a motor" . By that they mean that if the motor isn't smoking or hasn't smoked in the past you have a good chance of saving it. Check all of the connections. Make absolutely sure that all of the connections are good. Connect the volt meter with the red wire to the positive and the black wire to the negative wire at the motor. Drop the anchor over the side in the slip to put some load on the motor and then haul it back on board while watching the volt meter. It should drop some but not tank. If you get 10 or 11 volts, that's an unacceptable voltage drop. Change the circuit breaker out for a new one as they do go bad. Change it out with another one from, say, your spot light or deck lights or some other high amp switch to see if it still trips. Do the same with the foot switch or what ever you use. Check the solenoid also. The contacts in it might be going bad as well. Anytime you have a bad connection or some contacts are not making up right heat is produced from that high resistance. Electricity can't get past the dirty contacts or over the loose connection without producing some heat. That heat makes the contacts or bad connection get worse. That causes a voltage drop to the motor which will cause it to run slower then intended. It goes round and around getting worse and worse until something burns open. I hope this helps. I tried to keep it simple because electricity messes with peoples heads. It the nature of the beast. Good luck