Batteries are good; I pulled them and brought them in to check and they're fine. When idling I get a good reading on my voltmeter at ~13.5, but when I am running it slowly starts climbing as high as 16+. This happens with either battery and verified by my multitester. It sounds like the voltage regulator or rectifier is going bad, but I don't know how to test this or even where they are on this engine. I admit I don't even know enough to be dangerous, so any help that keeps me from being dangerous would be greatly appreciated. Thank you.