Help explain electrical components

[arp35]

In the attached picture, I am guessing the large cylindrical item is the starter solenoid that connected the key switch to the engine. If the engine I use (Kohler 25 w/electric start) already has a starter solenoid then I will discard this one...correct? What is the small rectangular item next to it (voltage regulator/rectifier)? It had a red wire coming off the starter solenoid and then another red wire going to the lights or ignition switch? Any ideas?

Hustler 950 Restoration - Amphibious ATV Pictures

[racerone3]

the cylinder shaped one is the solenoid, and if your engine has one you will not need this one. the other is a circuit breaker... it will get hot and open if there is too much current draw on it, then reset when it cools. if you do eliminate this solenoid, you will need to extend the wire from the breaker to reach battery + and also extend the exciter wire back to the solenoid on your engine. wiring wise, it would be easier to remove the solenoid from the engine, and use the existing wiring

[arp35]

Thanks for the info. I had not thought of it being a circuit breaker. I looked at it closely and all it says is AUX on the side. That is also a good point about the solenoid. If I use the engine one then I will have to run the heavy battery positive cable back to it. Hmmmmm...