Sean, 
You don't say in your post whether the pump spins up or not when/before 
the fuse blows.  My pump usually "freezes" up between Winter and Spring, 
due to the lack of internal lubrication (water) no doubt.  The current 
flow through the pump switch isn't enough to "unfreeze" it so I snake my 
battery cables over to the pump after attaching them to the battery.  
Then I use a pair of short leads from the cables to the pump to supply 
full voltage to the pump.  This usually gets it spinning again and I have 
no problems with it the rest of the season.

What I would suggest is that you pull the fuse and just run the leads 
from the battery cables direct to the inputs to the pump.  At least that 
way you can test the pump and see if it's the culprit.  It may be fried 
and have a dead short internally causing the fuse to blow, in which case 
replacing the pump will solve your problems.  If the pump is ok then 
you'll need to start tracing wires with a DVM to see where the short is 
occuring.  More than likely a frayed wire is coming in contact with a 
body panel somewhere.

Jack