My mower has 50 hours on and has worked fine until today. I turned the key to start it and I basically double clutched the the starter by accident. Now nothing happens when you turn the key.
There is a goop called "Liquid Electrical Tape".
I go through about 4 cans of it a year.
It is a thick plastic that forms an air & moisture tight cover over things like battery terminals & ground points.
I use glue lined heat shrink tubing. It's a bit more expensive than regular heat shrink tubing, but it's incredibly effective. Go with #2 marine rated cable and use these lugs: