Motor Draining Battery?? Opener Trip at risk

[scobec]

If I disconnect all wires to my battery, reconnect just the positive that goes to my motor and then put my meter between the negative battery post and the ground wire to by motor I measure 3 amps! That's a lot of current. I verified that the two engine wires do in fact go to directly to the motor.

The current draw goes away if I disconnect the ground from the engine block. Disconnecting the positive from the starter, unplugging all the connectors I could find and pulling the fuses on the engine didn't help.

I have a 4 stroke, 150hp outboard merc.


I can't get my boat into the dealer before I need to leave for opener, so I'm desperate for ideas.

[Wildcat Dude]

Need SN#

[EuropeanAM]

Please see the Announcements at the top of the forum, and provide your Engine Serial Number when posting. Thanks!

SOME draw is normal. But NOT 3 amps.

I do not recommend much of the testing you have been performing. You've been disconnecting a lot of critical connections.

When testing DRAIN or DRAW, it should be done with everything EXCEPT the positive cable connected. Measure between the POSITIVE cable and the battery.

It's also IMPERITIVE that you ensure the key switch and/or keypad are fully OFF. Any dash device that is ON will increase the current draw (and YES, the keyswitch, instruments, and keypad (if equipped) power from the ENGINE'S power supply).

More info may be available once you've provided your serial number, reconnected all these critical connections PROPERLY, and tested EXACTLY as suggested above.

[scobec]

Thanks for all the input.

I did everything that was suggested. The 3 Amp drain went away when I disconnected the positive cable from the alternator. Then with the main engine cables connected to my battery, I put my meter between the the cable and the alternator and could measure the 3 amps.

Alternator 1.jpg

If I disconnected the plug that goes into the alternator then I couldn't measure any current flow from the cable to the alternator.

Alternator with plugs pulled.jpg

I then measured the resistance between the alternator terminal and its housing. The resistance was 23Kohms ( maybe it was 20 ohms, I didn't pay close enough attention.

Alternator to ground resistance.jpg

So what does everybody think now?

[scobec]

SN 1B923588

Model Number 1150F23HD

[EuropeanAM]

I would suggest reconnecting EVERYTHING properly.

LEAVE the large RED (output) lead off the alternator (this should be the ONLY item disconnected).

Turn key ON, then TURN KEY OFF.

Wait 15 minutes (time this with a watch).

Recheck for drain between the alternator output post and cable at that time. If NO DRAIN is noted (or very minimal)- this is NORMAL.

IF the drain is still present, Disconnect the 14-pin harness connector COMPLETELY from the engine, and re-check for any drain (again).

Your results (above) are indicating that something is keeping the alternator "excited" (may simply be the MPR time-out feature that's standard with "Smart-Start" engine models).

[scobec]

I did the test and the 3 amp drain is still there. I found that the 2-wire plug has a constant 12 volts. Is that normal?

[EuropeanAM]

I did the test and the 3 amp drain is still there. I found that the 2-wire plug has a constant 12 volts. Is that normal?

There should be a constant 12V power on the RED wire. Purple wire should only have power when the key switch is ON (or MPR active/closed).

Verify that you had power on the purple wire, WITH THE 14 pin Keyswitch Harness plug DISCONNECTED from the engine.

If so... locate the MPR (Main Power Relay)... and disconnect it to see if the power problem disappears (relay MAY be hung closed).

[scobec]

I pulled the 14 pin harness and the 2-wire plug still has 12 volts. If I pull this plug the 3 amp drain stops.

[EuropeanAM]

Verify that you had power on the purple wire, WITH THE 14 pin Keyswitch Harness plug DISCONNECTED from the engine.

If so... locate the MPR (Main Power Relay)... and disconnect it to see if the power problem disappears (relay MAY be hung closed).

See RED text above....

[scobec]

Problem solved. It was the alternator. Even though my warranty expired in March, Mercury and Rapid Marine in Ham Lake, MN took care of it, Free of Charge

[Wildcat Dude]

Good deal