2001 Merc 200 EFI Killing Cranking Batteries

[fledderw]

I have a 2001 Mercury 200 EFI serial #OT334140 rebuilt in 2015 thru the Mercury remanufactured power head program.

This year it appears the alternator and charging system may not be recharging my cranking battery. After about 8-10 hours of running, the motor tries to shut down when I use the trim due to low power on my battery. Then the cranking battery does not have enough power to even turn the bendix to start the motor or barely work the trim. Checking out the battery voltage is 11.7 and load testing indicates amperage is down to 11%. This is with a brand new battery I purchased this year. I brought back to the dealer and he checked it out and determined it was bad and gave me a new one. I installed it and the same thing happened again after 8 hrs of use. The dealer then gave me another new one that I am using now and told me to check
and write down the voltage after each run.

These batteries are Northern standard cranking batteries having marine and cold cranking amperage beyond the requirements for this motor.

Another detail is that I had my boat transom rebuilt last winter, which required removal and then replacement of the engine. It could be possible that a connection was missed or incorrect when they reinstalled the engine after the transom rebuild.

Other than that, the engine runs perfectly throughout the whole RPM range. There is no signs of ignition misfire. The tachometer works fine. All electronics on my boat work fine.

My guess is an issue with the stator, trigger, or voltage regulators. Both voltage regulators were replaced in the 2015 rebuild. I have the full service manual for this engine but a lot of it is over my head. I do not have the required tools for diagnosing the regulators. Highest probability would be voltage regulators as this model engine has a reputation for that.

I would like to hear anyone's thoughts on this before I pull my rig out and take it to the dealer. Thank you.

[jbh3]

"These batteries are Northern standard cranking batteries having marine and cold cranking amperage beyond the requirements for this motor. "

Don't know what the spec's are for this particular battery and what accessories you run during the day, but it could be that your battery is simply lacking in Reserve Capacity. Do you start the day with this battery being fully charged? Your service manual should provide instruction for checking the output of the alternator. I believe all you would need is a digital volt meter. Hope you get it figured out.

[SilverFox579]

Have you checked voltage at the battery with engine running? ANY battery will lose capacity if engine charging system isn't functioning. "Northern standard cranking battery" isn't very descriptive, tell us what specific battery you have, group size, cold cranking amp capacity, reserve capacity, etc.

[JOE54]

check all fuses side mounted regs have fuses

[fledderw]

My Northern battery has 800CCA and 1150MCA. I ran the voltage test and verified I am getting zero output from my alternator. The problem must be either the stator or the voltage regulators. The tachometer works fine off either regulator.

[JOE54]

you can test stator output