There are two different deck configurations depending on serial number of the mower. Since 1 shows 3 different idler pulleys, but one of the 3 subs to the same as another so basically making it 2 small and 1 large. Now I was looking at the deck rebuild kit and shows the GY20996 for the 2002-2004 and the GY2099X48B for the 2005 But all the idler pulleys one way or the other sub to the same 3 pulleys with the belt being different between the years.
The fuse melting would be resistance in that area. So corrosion on the fuse or the fuse holder would result in the fuse melting. But also keep into mind that the electric clutch could have a partial short causing excessive current draw leading to that issue also if that is the weak link.