It supplies voltage to a number of items...
Here is probably the easiest way to test that I know.....
First....I am assuming that it blows when you turn on your key. It the engine has to be running, then this way will not work very well.
Remove the fuse and somehow connect a 12v test light across the contacts of the fuse holder.
If there is a consistant short, when you turn the key to on, the test light will light......DO NOT START THE ENGINE.
Then start unplugging the powered items...when the light goes out, you will have found the source or the direction of the source of the fault. When you unplug them, check for any corrosion that may be occurring...
Unplug the three pin connector from the alternator.
Unplug the a/f relay.
Unplug the iab control valve
Unplug the red four pin connector from the data link (or service port). It may have developed some corrosion in the contacts.
Unplug the 6 pin connector of the main wiring harness/next to the round 14 pin connector (front starboard side of the powerhead). Those wires go to your PGM and Charge lights.
If the fuse blows only while the engine is running, then definitely disconnect the 6 pin connector on the wiring harness by the 14 pin connector. Then you can run the engine......you just will not have a PGM or Battery Charge light. Be sure to remove the light and replace the fuse. If the problem goes away, there may be is a short to ground in the wiring harness near where it runs out of the engine....maybe only making contact when the engine is turned a certain way.
The following link goes to Honda's website to download an owner's manual. One the last couple of pages, you will find the wiring diagram....and you can check the routing of the wire firsthand.
http://cdn.powerequipment.honda.com/marine/pdf/manuals/31ZY6603.pdf
Good luck on your quest.
Mike
