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When you hook up the battery wrong in addition to the fuse it usually blows the diodes in the voltage regulator. Try disconnecting the voltage regulator then reconnect the battery, turn on the key to the ON position and see if the fuse blows.
#26 in the diagram on this page, http://www.boats.net/parts/search/Yamaha/Outboard/2001/VX150TLRZ/ELECTRICAL%203/parts.html
I wasn't on when the phone call request came through. Did you find the voltage regulator?