Do I need a new altenator? How do I to determine if my 2004 75 hp 4 stroke mercury outboard is charging my new batteries? We bought new batteries (ENGINE and Trolling) last year and they won't start the mercury engine afte an hour of fishing.

Question

Do I need a new altenator?  How do I to determine if my 2004 75 hp 4 stroke mercury outboard is charging my new batteries?  We bought new batteries (ENGINE and Trolling) last year and they won't start the mercury engine afte an hour of fishing.

Accepted Answer

Below is instructions on how to check your alternator:1. Check the battery Before you can tell if your alternator is working correctly, you need to see what's going on with your car battery. With the engine off, connect the positive side of your voltage meter or multi-meter to the positive terminal of your battery, and the negative side to the negative terminal. The reading should be about 12.7 volts. If it is below 12.4 volts, the battery may need replacing.2) Check the alternator voltage Turn on your engine, but don't press the gas. When the engine is on, the alternator is supposed to send electricity to the battery. Check your voltmeter or multi-meter again and read the voltage. If your alternator is working, the voltmeter should read between 13.8 and 14.2 volts.3) Check the alternator amperage Disconnect the voltmeter and connect an amperage meter (if you aren't using a multi-meter) to your battery the same way as you connected the voltmeter. Turn on all the electrical equipment in the car: lights, stereo, wipers and everything else you can. Let the engine idle at around 1200 rpm. Check your car's manual or parts manual to see what your alternator's maximum amperage should be. The amp reading on your meter should be near the maximum output. A 90-amp alternator will output approximately 88 amps. If your amperage is too low, then you probably need a new alternator.

Manufacturer	DB Electrical
Brand	DB Electrical
Model	400-12303
Item Weight	7.7 pounds
Product Dimensions	4.64 x 3.82 x 4.64 inches
Country of Origin	China
Item model number	400-12303
Manufacturer Part Number	400-12303
OEM Part Number	ADR0318
Amperage	50 Amps
Voltage	12 Volts

DB Electrical Alternator for Mercury Marine Engine 115ELPT Optimax

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