Too much voltage?

[NewNitro]

1986 200 mercury SN A914326 in years past the maximum voltage on cranking battery i've seen when running flat out was 13.7 Today at the start of the morning it was 13.0 at idle and within a half mile at full throttle it had gone to 14. and climbing. I watched it get to 14.5 and slowed to an idle and just fished the area and called it a day. I've replaced all the batteries with Interstate this spring. the cranking battery is a 27M. I did notice when i unplugged the Minnkota Digital 3 bank charger this morning the starting battery wasn't blinking green but showed 12.5 on voltmeter and 13.0 on HDS 8 at idle. Is there a maximum that the battery can take as far as voltage and should i be checking the rectifer or could it be that since battery wasn't fully charged caused the spike in voltage running up the lake? All connections are clean and tight

[lpugh]

14.5 is getting close to what I consider a max of 14.8. Test the battery to be sure it is good. High resistance in the battery will cause the charge voltage to rise faster than normal and still not achieve a full charge. I would check the voltage at the battery and the alternator with a DVOM to be safe. Usually due to voltage drops in circuits the HDS will report lower voltage than what is actually at the battery. If voltage is to high perform drop test on all circuits involved esp. the grounds. Poor regulator grounds can cause high output voltage on many systems.
Are you using a AGM battery or deep cycle? If you are you might want to rethink that, though I don't believe it would cause a high voltage charge rate, it may cause high current flow which would cause other issues

[JOE54]

some of the early 2.4 200 mtrs had a top mounted reg just behind flywheel bad about going out,watch your voltage if it gets over 14.5 ish your can bet its bad, good news is they NLA from MERC , oh if that 27m is a deep cyle need to get it off of stator type charging system, that's a troll batt,

[NewNitro]

some of the early 2.4 200 mtrs had a top mounted reg just behind flywheel bad about going out,watch your voltage if it gets over 14.5 ish your can bet its bad, good news is they NLA from MERC , oh if that 27m is a deep cyle need to get it off of stator type charging system, that's a troll batt,

The battery says cranking on it and from what i gleaned from the Lowrance forum one that was a favorite for starting and running accessories. I'm not following what you mean by the good news is it's no longer available from MERC. Where would i find another?

[JOE54]

cranking is good, really bad news ,I don't know at this time may try parts for sale on here

[NewNitro]

Update: Ran the boat for a long run and it still kept raising the voltage until I hit 14.5 and stopped. Went to local marine store and bought new rectifier. It still overcharges above 4000 rpms. Brand new Interstate 27M battery that was put in the boat in March. I fish 3 days a week on average and no problems until this started last week. When the battery was first installed it would show 12.9 on the graph when running and at end of day would be at 12.4. Then last Wednesday it suddenly started this overcharging mode. Any other ideas? Thanks

[CatFan]

Update: Ran the boat for a long run and it still kept raising the voltage until I hit 14.5 and stopped. Went to local marine store and bought new rectifier. It still overcharges above 4000 rpms. Brand new Interstate 27M battery that was put in the boat in March. I fish 3 days a week on average and no problems until this started last week. When the battery was first installed it would show 12.9 on the graph when running and at end of day would be at 12.4. Then last Wednesday it suddenly started this overcharging mode. Any other ideas? Thanks

14.5V could not be more perfect. You are trying to fix a charging system that is working. 12.9V is way too low.

[NewNitro]

I understand what you’re saying but it will go beyond 14.9 if I let it. The graphs upper most range is 14.9 and don’t want to burn it up. What scares me about it is the fact that it gets to 13.2 after 10 minutes of running and then goes to 14.9 in less than a minute. I will have someone available tomorrow to check the actual battery voltage while running, obviously can’t do that alone but at idle the volt gauge, graph readout and dvom all read the same

[EuropeanAM]

You stated in Post#6 that it hit 14.5V and stopped.

Voltage should not EXCEED 14.6 VDC. You can run safely at 14.5 all day long... even 14.6 and be just fine.

[NewNitro]

You stated in Post#6 that it hit 14.5V and stopped.

Voltage should not EXCEED 14.6 VDC. You can run safely at 14.5 all day long... even 14.6 and be just fine.

Not it being contrary, but I should have said it hit 14.5 and I stopped. Checked the Lowrance forum and found out 14.8 was top range for graph and tried it again. I feel certain it will go to 17 volts or more if I let it. I’m really stumped why it takes awhile to get to 13 volt range and then in a matter of seconds jump to 14.5 or more.Taking battery out tomorrow to get load tested, starting to suspect a defective battery.

[CatFan]

Not it being contrary, but I should have said it hit 14.5 and I stopped. Checked the Lowrance forum and found out 14.8 was top range for graph and tried it again. I feel certain it will go to 17 volts or more if I let it. I’m really stumped why it takes awhile to get to 13 volt range and then in a matter of seconds jump to 14.5 or more.Taking battery out tomorrow to get load tested, starting to suspect a defective battery.

Not sure why you think the graph can’t handle more than 14.8V. They can handle 17V.

[NewNitro]

Not sure why you think the graph can’t handle more than 14.8V. They can handle 17V.

You’re right CatFan, I have no idea where I got 14.7 for the graph. Getting old isn’t for sissies. Lol. In post #9 EuropeanAm says to not exceed 14.6 but he didn’t say whether that’s for the battery’s sake or charging system. I hope he sees this and explains.?

[CatFan]

You’re right CatFan, I have no idea where I got 14.7 for the graph. Getting old isn’t for sissies. Lol. In post #9 EuropeanAm says to not exceed 14.6 but he didn’t say whether that’s for the battery’s sake or charging system. I hope he sees this and explains.?

He's referring to the output of the charging system.

[NewNitro]

Not familiar with charging systems on a boat. So far I have a new battery and rectifier and the problem still exists, where should I check next? I’m not relying on trusting a new battery to not be defective.

[leonreno]

Your stator supplies the power to your regulator, it’s the regulator’s job to keep voltage below 14.6. What regulator did you buy? Mercury or aftermarket? I do not know if a bad stator can cause a good regulator to supply over voltage. Though I do believe a bad stator can damage a good regulator. Have the new battery load tested to eliminate that problem. Double check all grounds/connections on the motor and battery.

[lpugh]

I do not have a wiring diagram for that motor, but all regulators must have a circuit that senses battery voltage, later system have a red wire from the start solonoid to the regulators. It would be wise to voltage drop test that circuit as well as the regulator grounds. Any voltage drop in those circuits will cause high charge rates. Don't guess test first

[EuropeanAM]

This old gal uses a separate rectifier and regulator (two separate components) as I recall.

I have not seen you say: "I took it out on the water and ran it for 30 minutes, monitoring and the voltage reached X" (Where "X" is > 14.6 VDC), since you replaced the components. You've just been saying that you think it will.

Need to verify there is a problem, before trying to fix it.

[NewNitro]

I can’t say that I ran it for 30 minutes because it gets to the 14.9 threshold in ten minutes at 4000 rpm and less than that at WOT. Should I run longer than that and see where it peaks out?. I just was afraid of burning something else up if I ran over 14.9 too long.

[tomoad]

Yes run it. I had a 88 200 one time and it had a bad regulator & it was putting out 16+ volts. I always figured 14.5volts was charging, it’s not over charging.

[EuropeanAM]

You also need to be reading the voltage AT the battery, with a DVOM (Digital Volts/Ohms Meter)- yes, you may need to rig up some extension leads to accomplish this SAFELY.

For this purpose, don't trust gauges or other "loaded" devices such as graphs.