The last couple times out last year I had some problems with starting. Every once and awhile I'd turn the key and nothing would happen. I figured either my starter or solenoid were going out. No big deal just replace it. After doing some research I found out it could also be another solenoid on top of the engine that some people are calling a slave solenoid. Whats the difference between this solenoid and the on mounted on the starter? What does each one do? Should I just replace the starter anyway for peace of mind?