Motor draining battery

[el_bany2005]

Hi, I am new to the forum and to boating as well. I owned my first boat 17' cc proline that came with a 90hp 1996 Force outboard.
The motor starts fine and runs pretty smooth, but I noticed that the battery drains to fast even when the motor is running.
Yesterday I charged the batteries fully, put the boat on the water, started the motor and ran for about an hour. When I returned to the ramp turn off the motor and tried to started again and the battery was dead. I am suspicious that the motor is not generating his own electricity and its taking the power from the battery.

I recharge the battery and started the motor at home, then disconnected the + cable from the battery and the motors turned off. Is that suppose to happen?
I would think that the magnets below flywheel create electricity and once the motor turns over and starts rotating the battery does not play any role on keeping the motor running.

Please let me know what you think about this issue?

 

[Barnacle_Bill]

Re: Motor draining battery

Never run the motor with the battery disconnected as it will blow your rectifier/regulator. But I suspect it was already bad. Test it.

 

[Justinde]

Re: Motor draining battery

Test the battery- load test it...... Start with the basics, then move up. Does the alternator charge?? You can test for that too, but simply check the battery first, and go from there ;-)

 

[MickLovin]

Re: Motor draining battery

I would start with your battery by testing it with a hydrometer, also check to see if you have an a/c voltage coming from the magneto of your flywheel, my outboard and most chrysler outboards charge at a rate of 10 amps at 5500 RPM and don't cut in untill 1000 RPM.
I am not sure about what you are asking about the motor turning off, as mine will turn off if I turn the battery off as it takes power of the ignition and the cdi. I would suggest what bhile is saying may be the case about your rectifier/regulator, it rectifies the a/c volts coming from the flywheel and regulates the voltage to a suitable charging voltage. But check your battery first easy test, take it to a local battery shop for a load test or self test with a hydrometer. Hope this helps. As I say not that familiar with the force.

 

[pnwboat]

Re: Motor draining battery

You are correct that the battery is not necessary to keep the motor running on the Force motors that use the Prestolite or later Mercury Thunder Bolt capacitive discharge electronic ignition systems. The only thing the battery does is to supply voltage to operate the starter and any accessories. Once the flywheel starts spinning, the interaction of the flywheel magnets and the stator create the voltage for the ignition system. Under normal operating conditions, disconnecting the battery should have no affect on a running motor....other than possibly causing an unstable load for the rectifier/regulator.

As mentioned above, you need to check the battery itself. If it's OK, then check the output voltage of the rectifier/regulator. It should be around 14.5 volts DC at a minimum of 2000 RPM's. Also verify that all the battery cable ends are absolutely clean both on top and the bottom. Clean them off so that there is no corrosion or oxidation.

If that all checks out, then start disconnecting accessories by pulling individual fuses on your fuse panel, (if you have a fuse panel). You may have a shorted out light or light socket that is draining the battery, or some other item that is malfunctioning, or a short in the wiring.

 

[oldboat1]

Re: Motor draining battery

know the magneto motors with electric start don't need a battery, other than for starting, but not sure about yours. ( My '72 55 didn't even have a charging system.) It's easy to check to see if your rectifier is blown and needs to be replaced, if you have a voltmeter. I have a "portable" voltmeter gauge for testing, and a state-of-charge tester that I bought somewhere. If the battery has an 80% charge before starting the motor, then goes up to 100% while the motor is running, the charging system is working. Whether it's charging sufficiently is another issue, but if you are seeing a charge you will know the rectifier is working. Certainly, if the battery is being discharged somehow, that would show up with a voltmeter too. To have a dead battery when you get back to the dock, the discharge rate must have been greater than the charge rate. But none of that is a very technical answer....

 

[el_bany2005]

Re: Motor draining battery

Thank you all for your inputs. I took the battery to the autoparts and it tested ok. It is rated 500 CCA and tested 558CCA. I understand that if the voltage regulator is bad, the battery is not going to be charged while the motor is running, but would that mean that it will drain it?
I will move up on the troubleshooting procedure and check if there is voltage at the output of the regulator, if there is I am then inclined to think that there is something else draining the battery (shorts in the wiring/accessories) at a rate greater than it is been charged. Will have to wait for the repair manual that I ordered from this site for schematics and wiring diagrams.

 

[el_bany2005]

Re: Motor draining battery

You are correct that the battery is not necessary to keep the motor running on the Force motors that use the Prestolite or later Mercury Thunder Bolt capacitive discharge electronic ignition systems. The only thing the battery does is to supply voltage to operate the starter and any accessories. Once the flywheel starts spinning, the interaction of the flywheel magnets and the stator create the voltage for the ignition system. Under normal operating conditions, disconnecting the battery should have no affect on a running motor....other than possibly causing an unstable load for the rectifier/regulator.

As mentioned above, you need to check the battery itself. If it's OK, then check the output voltage of the rectifier/regulator. It should be around 14.5 volts DC at a minimum of 2000 RPM's. Also verify that all the battery cable ends are absolutely clean both on top and the bottom. Clean them off so that there is no corrosion or oxidation.

If that all checks out, then start disconnecting accessories by pulling individual fuses on your fuse panel, (if you have a fuse panel). You may have a shorted out light or light socket that is draining the battery, or some other item that is malfunctioning, or a short in the wiring.

This is a question for general knowledge. If the stator/flyweel interaction is not creating any energy for the ignition systems to work, is it possible then that the ignition system could be taking that energy from the battery?
I know that one should not run a motor with a disconnected battery, but I did that quick test just to see what happened. If the motor does not need a battery to run other than to provide the start how to explain then that it stopped running when I disconnected the battery? I tried that twice and it did the same.
Thanks!

 

[pnwboat]

Re: Motor draining battery

Yes that is odd that the motor stops when you disconnect the battery. You did say it was a 1996 90HP motor? If this is correct, then I suspect that you may have an issue with the rectifier/regulator. The stator not only contains the windings for the ignition system, but it also has the battery charge windings and they are in close proximity to each other. A defective regulator can affect the ignition voltage output of the stator. Disconnecting the rectifier/regulator is one of the standard tests for an ignition miss.

Check the output voltage of the regulator and see what you get. If you really want to test, you can disconnect the two Yellow wires that come from the stator and connect to the rectifier/regulator. This will eliminate the rectifier/regulator from having any affect on the ignition system. Disconnect the battery with it running and see what happens.

You can also check the stator itself with an OHM meter. Disconnect the Green/White and White/Green stator wires that come from the stator. These are the connections from the stator ignition coil windings. Measure the resistance between them. It should read between 500 - 700 Ohms. You can also check the resistance between the two Yellow wires that connect to the rectifier/regulator. They should measure .5 - .6 Ohms. Almost a dead short, but not quite.

 

[gm280]

Re: Motor draining battery

It does sound like your rectifier is bad. And that is the reason the motor stopped when you removed the battery supply that was keeping the ignition running. I think you had it all figured out all by yourself there... You can take the rectifier and ohm it out as well to verify your thinking. Just remove the wires (mark them for reinstalling them back though) and read the input to output wires on the ohm scale. There are other posts on here that describes this better then I can retype it all out... Just search for testing rectifiers. I suspect it is open...that would be my guess!

 

[Nordin]

Re: Motor draining battery

Sounds really odd that the engine stops when you disconnect the battery!!!!!
The stator that supplies the ignition system generate a AC current and the voltage is about 150-180V high. Then this voltage is rectifiered to DC and stored in a capacitor in the CDI box.
The battery cannot supply the ignition.
The stator and the alternator are to separate windings but they are in the same package under the flywheel.

BTW The draining can be done from accessories.
If you have a VOM that can measure current then check if current is flowing when everything suppose to be off. You can also check to disconnect the + wire at the battery when everyting suppose to be off and then touch the wire to the + pole. If it arcs then something is draining.

 

[el_bany2005]

Re: Motor draining battery

Ok, I will troubleshoot the Voltage regulator/rectifier. Will check if there is input from the stator and if there is output from the regulator. Those two measurements will tell me where to move next. Don't really suspect the stator since the tachometer is working OK so:
1- AC Input and no DC output will tell me the that rectifier/regulator is bad, therefore batteries are not charging.
2- No AC input will reveal a problem on the charging system coils on the stator.
3- AC input and DC output will tell me that there is something else on the accesories probably that in ON all the time. BTW I only have a stereo(no amplifier), a fishfinder, and a VHF radio, then the nav and anchor lights.

Will post later maybe after the weekend with some results.

 

[el_bany2005]

Re: Motor draining battery

Yes that is odd that the motor stops when you disconnect the battery. You did say it was a 1996 90HP motor? If this is correct, then I suspect that you may have an issue with the rectifier/regulator. The stator not only contains the windings for the ignition system, but it also has the battery charge windings and they are in close proximity to each other. A defective regulator can affect the ignition voltage output of the stator. Disconnecting the rectifier/regulator is one of the standard tests for an ignition miss.
Check the output voltage of the regulator and see what you get. If you really want to test, you can disconnect the two Yellow wires that come from the stator and connect to the rectifier/regulator. This will eliminate the rectifier/regulator from having any affect on the ignition system. Disconnect the battery with it running and see what happens.
You can also check the stator itself with an OHM meter. Disconnect the Green/White and White/Green stator wires that come from the stator. These are the connections from the stator ignition coil windings. Measure the resistance between them. It should read between 500 - 700 Ohms. You can also check the resistance between the two Yellow wires that connect to the rectifier/regulator. They should measure .5 - .6 Ohms. Almost a dead short, but not quite.

That test makes sense, that would take the regulator/rectifier out of the equation.
So DC output from the regulator should be 14.5V at 2000 rpm and how much AC input (between the two yellow wires) I should expect coming from the stator at the same RPMs?

 

[pnwboat]

Re: Motor draining battery

With the Yellow wires connected to a good working rectifier/regulator, you typically see 16 - 18 volts AC. I can't recall if I've ever checked the AC voltage with the Yellow wires disconnected though.

 

[el_bany2005]

Re: Motor draining battery

Yesterday I did some more testing, I repeat the experiment where I disconnect the the Batt while engine running and it did not stop, so not really sure why it did it before, but not really concerned about it.
I measured DC output on the regulator and there was voltage, but jumping around rapidly even going negative sometimes. Does it mean its bad? Any other diode testing that I could do to confirm?
I also check continuity on the two yellow wires from the stator. There is no short between them, neither one of them is shorted to ground.
Also measured the AC input between disconnected yellow wires while the engine was running, but it was jumping around also and very big values, not sure if that was an accurate test since I have read that my meter should have a DVA option in order to check stator voltage.
I still having the same issue: A fully charged battery that tested ok would die after a few cranks, and sometimes I can see the starter hesitating or not strong enough to spin the flywheel, so I am starting to think that it could be a battery not being charged by regulator/bad starter combination.
Any inputs?

 

[pnwboat]

Re: Motor draining battery

I measured DC output on the regulator and there was voltage, but jumping around rapidly even going negative sometimes. Does it mean its bad? Any other diode testing that I could do to confirm?
The D.C. voltage should be fairly stable. Shouldn't change more than 1 volt at the most I would think. There is no diode check since the components are sealed inside the epoxy or what ever material they use. You cannot get to the components to check them.

I also check continuity on the two yellow wires from the stator. There is no short between them, neither one of them is shorted to ground.
What was the actual reading in ohms? It should read around .5 ohms.

Also measured the AC input between disconnected yellow wires while the engine was running, but it was jumping around also and very big values, not sure if that was an accurate test since I have read that my meter should have a DVA option in order to check stator voltage.
The A.C. output voltage can be read with the meter without the DVA and it too should be fairly stable. You should see around 16 - 18 volts A.C. at 2000 RPMs.

Basically what you've done so far is confirmed that you have an issue with the battery charging system on your motor. It's important to note the actual resistance readings on the battery charging windings (two Yellow wires). It's very low resistance and should almost appear to be a short.

Check your ground wires. The regulator/rectifier has to have a good ground reference to work properly. Sometimes it has a separate Black ground wire, sometimes the metal case has to be making good contact with the plate that it's mounted to.

There should be a Black ground wire that runs from the plate that the rectifier/regulator and coil packs are mounted on to the engine block. Make sure you have a good solid connection on that wire.

Also check the bullet connectors on the two Yellow wires. Seen many of them where the clear plastic insulator on them look burnt or overheated. They are typically crimped on. If they look like they've been overheated, discolored and corroded, it's sometimes difficult to get a good connection when taking voltage readings on them. Try reading the A.C. voltage between one Yellow lead and ground, then the other Yellow lead and ground. Compare that with reading across both Yellow leads.

Forgot to mention that slow starter cranking could also be caused by corrosion on the battery cable connectors. Check the battery cables (Neg. and Pos.). Where ever ther is a battery cable connection, remove it and take a wire brush and clean them off so you have nice shiny metal. Also the neg. cable should be bolted to the block. Make sure you have a good connection there.

 

[Big Fish Billy]

Re: Motor draining battery

Here is a couple overly simple tests and solutions. Test the battery voltage before starting, hopefully around 12 volts, start the engine, should go up to 13 or 14 volts, if not charging system has problems. Shut off engine. Now disconnect the positive cable(s)/wires from the battery, take the heavy duty wire first and touch the battery terminal, notice if there is a spark...repeat with any other wires that might have been connected there...any wire that creates a spark when you touch the battery terminal means there is a short/load on it, and thus the reason the battery is going dead. If you cannot find/isolate the problem/leak, install a Perko battery switch that shuts the battery off when not in use, until you do, good idea anyway. Bill

 

[MickLovin]

Re: Motor draining battery

Here is a couple overly simple tests and solutions. Test the battery voltage before starting, hopefully around 12 volts, start the engine, should go up to 13 or 14 volts, if not charging system has problems. Shut off engine. Now disconnect the positive cable(s)/wires from the battery, take the heavy duty wire first and touch the battery terminal, notice if there is a spark...repeat with any other wires that might have been connected there...any wire that creates a spark when you touch the battery terminal means there is a short/load on it, and thus the reason the battery is going dead. If you cannot find/isolate the problem/leak, install a Perko battery switch that shuts the battery off when not in use, until you do, good idea anyway. Bill

It may have to obtain a certain RPM before you notice a charge, the Chrysler is 1000 RPM before a charge current starts and it is 10 amps at 5500 RPM unsure what your force would be.

 

[el_bany2005]

Re: Motor draining battery

I measured DC output on the regulator and there was voltage, but jumping around rapidly even going negative sometimes. Does it mean its bad? Any other diode testing that I could do to confirm?
The D.C. voltage should be fairly stable. Shouldn't change more than 1 volt at the most I would think. There is no diode check since the components are sealed inside the epoxy or what ever material they use. You cannot get to the components to check them.

I also check continuity on the two yellow wires from the stator. There is no short between them, neither one of them is shorted to ground.
What was the actual reading in ohms? It should read around .5 ohms.

Also measured the AC input between disconnected yellow wires while the engine was running, but it was jumping around also and very big values, not sure if that was an accurate test since I have read that my meter should have a DVA option in order to check stator voltage.
The A.C. output voltage can be read with the meter without the DVA and it too should be fairly stable. You should see around 16 - 18 volts A.C. at 2000 RPMs.

Basically what you've done so far is confirmed that you have an issue with the battery charging system on your motor. It's important to note the actual resistance readings on the battery charging windings (two Yellow wires). It's very low resistance and should almost appear to be a short.

Check your ground wires. The regulator/rectifier has to have a good ground reference to work properly. Sometimes it has a separate Black ground wire, sometimes the metal case has to be making good contact with the plate that it's mounted to.

There should be a Black ground wire that runs from the plate that the rectifier/regulator and coil packs are mounted on to the engine block. Make sure you have a good solid connection on that wire.

Also check the bullet connectors on the two Yellow wires. Seen many of them where the clear plastic insulator on them look burnt or overheated. They are typically crimped on. If they look like they've been overheated, discolored and corroded, it's sometimes difficult to get a good connection when taking voltage readings on them. Try reading the A.C. voltage between one Yellow lead and ground, then the other Yellow lead and ground. Compare that with reading across both Yellow leads.

Forgot to mention that slow starter cranking could also be caused by corrosion on the battery cable connectors. Check the battery cables (Neg. and Pos.). Where ever ther is a battery cable connection, remove it and take a wire brush and clean them off so you have nice shiny metal. Also the neg. cable should be bolted to the block. Make sure you have a good connection there.

The two yellow wires from the stator measured 0.5 ohm as you said.Will have to try to get a better AC reading between the two yellow wires and each one to Gnd. The rectifier/Regulator ground is good (bolted to the chassis) and all + terminals on the starter solenoid looks clean. Also the bullet connectors look good on the yellow and red wires from the regulator.
Today I disconnected every accesory on the console from battery(They run from a separate battery anyways). The only connection left was from the cranking battery to the starter solenoid, when I disconnected the + wire on the battery and touched the post back on with the heavy duty red wire, there was a spark, meaning that something was drawing current or a short when I closed he circuit. Then I unplug the red wire from the regulator/rectifier and repeat the same test and there is no spark this time.
This test which left the rect/reg out of the equation plus my last test where I did not see a DC output from it when the engine was running points to a bad part, but I guess my question is if that could have drain a good battery so fast ? Thanks

 

[el_bany2005]

Re: Motor draining battery

Today I also check resistance on the starter solenoid terminal. Is it normal for the solenoid terminal that connects to the starter motor to have a low resistance to GND (1.5 ohms) when everything is OFF. I know that internally that terminal will connect to the battery (+) when the ignition key is turned, but I would think that it would be an open circuit (high resistance to GND) when everything is OFF.

I am trying to identify if I have a combination of causes for my charging issue. In the end there is not to many components in that path:
stator windings (AC) => rectifier/regulator(DC) => + terminal on the starter solenoid => + post on the battery.