Mercury 4 stroke poor charging

[Rzrjon]

I had a post where I asked for assistance troubleshooting whether or not my motor was charging the main batteries. I found that the motor was in fact charging however when using the big motor at low speeds I was still killing batteries. My last trip out I only ran 1 graph with the brightness turned down, no radio, and no livewell. Trolling around at about 3 mph within about 5 hours I had a low voltage alarm. At the end of the day I had to put the motor in neutral and rev up just to get it to trim up. I asked a mechanic who said that the gen motor I have (2015) uses a stator instead of an alternator and does not create enough charge at low speeds to even sustain itself. I asked about adding a battery and he said it will not fully solve my issue but instead just increase my run time. Talking to guys with yams and etecs they say that they rarely ever have to charge their main batteries at home. I have to charge mine after every outing. Wondering if anyone else has this issue since it is a pretty common motor. Are there any proper solutions?
Thanks

[REW]

RZ

What is the year and model motor that you are running?

How old is the motor?

The mechanic could be correct. However, you need to do some checking to verify that your motor is actually charging correctly.

You may actually have a defect in your charging system. The charging voltage and current supply needs to be chucked when the motor is running at 1500, 2500 and 3000 rpm to insure that the motor's charging system is actually in good shape.

You could have a defect in your charging system that is actually causing the problem.

You could also have a defective battery or batteries that are not actually charging well, even though the motor might be performing well.

1. Check the charging system of your motor.
2. Fully charge all batteries in the boat for 24 hours and then take the boat into a battery shop and have them load test each of the batteries for correct operation.
3. Finally verify that all of the electrical items in your boat are working correctly and that when not using the items are actually turned off and not drawing any current. To be sure, put an ammeter in series with the main battery lead and see if power is going out of the battery or coming into the battery when you are trolling.

You may or may not have an actual problem that - if fixed would solve your problem. But, as the mechanic suggested, it is possible that the motor is just working correctly and will not charge your battery at the engine rpm you are running.

Best wishes

[Rzrjon]

The batteries are new and have been replaced twice. I did do a check for grounds to verify the batteries are properly isolated. As for the checking the charging I had the boat running with a volt meter attached to the battery itself. I watched the meter climb from 12.2 up to about 13v as i throttled up in neutral.

[chico]

Your description is a little confusing, do you have a trolling motor on your boat...Chico...

[Rzrjon]

I do have a trolling motor however when on the bigger water trolling faster I use the big motor.

[Ozark Bob]

Originally Posted by Rzrjon

I do have a trolling motor however when on the bigger water trolling faster I use the big motor.

What batteries do you have? Make and size. Bob

[TomP.]

I have a 55 amp alternator on my Opti running 2 Helix 12`s and livewell, I still need to charge my starting battery after every time out there is no way the alternator can put enough charge back into the battery unless running miles and miles.

They claim it takes 9 miles of driving to recharge a car battery after one starting cycle.

[chico]

Originally Posted by Rzrjon

I do have a trolling motor however when on the bigger water trolling faster I use the big motor.

Size and model of big motor?

[Lazy Ike]

Rzrjon - from a lead acid perspective.... at 12.2 the battery is quite discharged. In a great world you should see 12.6v charged w/o any draw. For comparison purposes typically a battery maintainer will keep you at / apply 13.3v ish at the final phase. Some may be a tenth higher at lower outside temps. 13.3 should be a target for you with the engine running and no draw.

Try to get details on engine charging output by rpm beyond "yeah it is working" so you know what you should see on the meter. Start with a charged battery. Note the voltage may change from just charged to cooling for some hours.

[Custom Eyes]

My guess is the stator. My 50hp Merc had one and my batteries never went low while trolling. 12.2-13V is really low for the engine running.