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ContinuousWave: Small Boat Electrical
Outboard Failure to Charge Battery
|Author||Topic: Outboard Failure to Charge Battery|
posted 07-31-2009 03:03 PM ET (US)
I have read some of the postings and responses on this website and am very impressed. I suspect this is a topic you may deal with a lot, but I hope you can help me.
I have a 2004, 40 hp, 4 - stroke EFI Mercury outboard. It has ceased charging the battery. As long as the battery is fully charged, the engine starts and runs fine, but, naturally the battery slowly discharges until the warning buzzer sounds. I have had the battery tested and it is fine. I believe that a common failure mode is the rectifier, but have also heard that it could also be the regulator or stator. What is it most likely to be? Where on the engine would I find the part/s and how do I test it / them?
posted 08-01-2009 08:30 AM ET (US)
Assume you checked battery voltage while engine was running and the battery charging circuit fuse?
If you have time to wait for delivery order a OEM Mercury Service Manual that covers your model if your local dealer doesn't stock it or ask for a copy of relative pages. Sometimes you can find them on eBay with a buy it now. The SM provides good pretty good detail for checking the components involved.
The only SM I have that's close is for the 75/90 EFI. On those only things in the system are the stator, regulator/rectifier(single unit) and associated wiring.
posted 08-03-2009 12:44 PM ET (US)
I checked battery voltage while engine was running and the battery charging circuit fuse. Checked the voltage with the boat's voltmeter and a handheld at the battery. No change showed when the motor was fired up or at standstill. I think I may have found the failed component though. Sqaure metallic box filled with an epoxy of sorts attached to the side of the motor looks like it's been fried! Taking it to a dealer.
posted 08-03-2009 12:58 PM ET (US)
That box is the rectifier.
$40 or less.
Plug and play.
posted 08-04-2009 01:02 AM ET (US)
Voltage Regulator for my 2001 75hp 2 stroke runs about $140.00.
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