Hustler 2500 maintenance question - Help please!

[AverageBear]

I have a Hustler 2500 that is driving me crazy this year. It have been a very dependable machine for several years and for over 300 hours, then the following started:

Driving along (mowing) and it dies
check fuel filter - fine
check gas - fine
replace battery

Mowing and it dies. won't crank
dealer determines the engine has seized up - replace Kohler 25 hp motor

Battery goes dead over a period of several days (parked less than one week
replace battery again
not sure what else they did

Battery goes dead over a period of several days and also when I shut down the engine the fuse on the ignition switch blows. I replaced the fuse with a high amp rated fuse (I know, dumb) and it melted the fuse case and blew the fuse after mowing for several hours
replace fuse holder and fuse
replace switch
replace battery again (I think all the batteries were probably fine.)
not sure what else they replaced

Battery continues to go dead over a period of several days. I mow half a dozen times for 1 to 3 hours without a problem other than having to jump start the engine if the mower has been sitting.

Today, I mowed for 2.5 hours, and then stopped to refuel. When I tried to restart the engine, it would not crank and the motor for the cooling fan did not run. The battery has plenty of charge and neither of the two fuses are blown. Can anyone give me a clue as to what might be my problem at this point?

[ed2150]

Post your message on the Hustler company-sponsored forum here on LawnSite, they're pretty fast to try and help out.