Fuse size in harness to Starter
 

What size of fuse should be in the harness that goes to the starter?
Currently there is a 10 amp fuse there but it is blowing out at times.

10 amp is normal dont go to a bigger size you have a short somewhere that your going to have to track down. I made the mistake of going to a bigger size trying to track a short and melted a bunch of wires that i had just redone. you can also get a 10amp relay that way when it trips it resets itself. It wont fix the problem but it will make it less of a head ache. It will take time to track down the short but take your time and inspect everything.

You just have to go through all wiring looking for a temp short or bad ground. Also check all plugs. Many times the pins may not be installed right barely making contact which will really heat up a circuit just as corrosion will do.