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2005 BF225 #5 10amp alternator fuse blows

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Leaky Tuna

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Been having trouble with my starboard 225. The #5 fuse (alternator) in the engine fuse box blows. My alarms show 'check engine', 'alternator' and surprisingly 'fuel separator'. I checked the fuel separator first and found nothing but gasoline (same for my inline filters). The engine will run but the alarm keeps beeping and it is not charging the battery (I know this because I turned off the battery switch and it stopped running). This happened a few times intermittently and I changed out the alternator. Ran fine for 2 days and then it happen all over again. Tested it back at the dock and it blew 3 fuses in a row. Fuses blew after it ran for about a 30sec or so. I figure I've got a short somewhere...any ideas?
 
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Disconnect the Alternator, put in a new 10A fuse and run the engine. If it does not blow, the line from the main Relay to the alternator regulator is good. (The 10A fuse is for the alternator regulator and the 150A fuse is the alternator main output).

If it doesn't blow, it would seem to be a problem with the alternator regulator, but this is built in with the alternator, and you have already replaced it.

The same 10A fuse that feeds the regulator is also common to: O2 Sensor Heater (item 47), IAB Valve (item 48), Fuel Cutoff Solenoid (item 49), Service Check Connector (item 35) and Panel Indicator Light (item 15), so if it blows it could also be any of these.

Try common logic approach with the attached schematic. You can either disconnect the listed items one by one to find the culprit or you can disconnect everything (all listed items + alternator + main relay off and remember the panel light too) and measure the circuit against ground, it should be open or infinite.
 

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  • Pages from Honda Shop Manual BF200A.pdf
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As a quickie, you can also try first before the above to disconnect the O2 Sensor and run the engine with the alternator connected and see if it blows. You will get the alarm and engine will run rough, but it is a quick way of eliminating a short in the heater.
 
Blacktimes said:
As a quickie, you can also try first before the above to disconnect the O2 Sensor and run the engine with the alternator connected and see if it blows. You will get the alarm and engine will run rough, but it is a quick way of eliminating a short in the heater.
Click to expand...

Thanks for the guidance. Will be working on it the next few days. Any idea why the fuel Water Level (separator)alarm is active at the same time?
 
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