99 Honda BF40 & charging

[wstu]

I have a 99 Honda BF40 and she does not seem to be charging the battery anymore. I have a battery monitor (Link 20) and she reads exactly the same amps while running at 2500 RPM's as when the engine is off. So, I need to replace the alternator (or whatever it is called) but I read that the newer engines have much better charging systems. Would it be possible to upgrade the charging system to the newer version? Also, is this a DIY project? Thanks all

Wayne

 

[cp]

Re: 99 Honda BF40 & charging

When you write that

...a battery monitor...reads exactly the same amps while running at 2500 RPM's as when the engine is off. Wayne

do you mean that you are reading ZERO amps? Because, with the engine OFF you will read neither charge coil amps or volts; the charge coil is not energized when the engine is OFF! If you're reading volts with the engine OFF, then you may be reading battery voltage, not charge coil voltage.

If you are indeed reading ZERO amps at 2500 rpm, then your charge coil may indeed be dead or more likely, your regulator/rectifier is. Suggest you check the regulator rectifier before considering replacement of the charge coil. The charge coil (alternator) has the same 10-amp rating for motors from BF50 to BF25, but since it is packed into the underside of the flywheel, it would seem unlikely that you would be able to upgrade to a larger, higher capacity coil.

 

[wstu]

Re: 99 Honda BF40 & charging

Thanks for the reply, I am reading ZERO amps on the monitor if the engine is OFF or ON. I thought the rectifier was the alternator but I guess I have both. Can you tell I am ignorant when it comes to engines

Wayne

 

[cp]

Re: 99 Honda BF40 & charging

On your model outboard, the charge coil ("alternator") is located under the flywheel and the regulator/rectifier is located separately under the cowl, mounted somewhere on the engine. Suggest you locate and check the rectifier for an open circuit, which would explain no charging current flow when the engine is running. Your owner's manual will have a wiring diagram which will show you which wires come from the coil (the AC input) and which wires go to the battery (the DC output) to help you in testing the rectifier. If you don't have an owner's manual you can find the one for your BF40 here, using your engine's serial number. If you are unsure of how to find and test the rectifier, then perhaps you should take the motor to a dealer for service/repair. Good luck.