BATTERY VOLTAGE PROBLEM PART 2-need help

[Bitesomthing]

Yamaha OX66 250 Motor 2001
well since my boat is only showing 12.8 volts at 4700 rpm i thought it my be the Batteries or the cables being corroded or the battery switch. So one by one i Changed out the Battery switch, cleaned all the cable ends and got rid of all wing nuts, Bought two brand new Trojan deep cycle batteries and after all that all i see is 12.8 when running. The voltage might sneak up to13.0 after a long run but the minute i use any electronic equipment it drops back down to 12.8. ANY IDEAS?
I did have a new brain put on the boat about a month ago, do you think that might have anything to do with it? Do the charging and brain unit even work together????
The boat voltage shows me 14.2/13.5 for about the first 1/2 hour of running
after i have charged the batteries on land after about that 1/2 hour though i never see 13+ volts again all day. i only run one battery at a time.
also when sitting out on the ocean i can check my volts after sitting on a spot for a hour or so and see the battery voltage at 11.6/11.4 volts. This low voltage is when running very little electronic equipment---- Fish finder, bait pump 7amps, music radio, vhf radio, and Gps unit.
Any help is taken here thanks
Chris


Almost seems like i have something drawing amps from the battery
that i don't know about. Is there a way to check if the battery has a amp draw on it when everything i know about is off??
HELP... this boat and its repairs are driving me NUTS!!!!!

Since i got such a great deal i had to
Replaced high preasure fuel pump
replace all fuel injectors
replaced Brain unit
and now this... I should Have bought a new boat instead of used.
Thanks again Chris

 

[DaleH]

The voltage might sneak up to13.0 after a long run but the minute i use any electronic equipment it drops back down to 12.8. ANY IDEAS?

Don't rely on OB gauges, check it with a digital multimeter.

I did have a new brain put on the boat about a month ago, do you think that might have anything to do with it? Do the charging and brain unit even work together?

It could.

The boat voltage shows me 14.2/13.5 for about the first 1/2 hour of running after i have charged the batteries on land after about that 1/2 hour though i never see 13+ volts again all day. i only run one battery at a time.

First off, you MUST wait at least 12-hours after charging a battery for the 'surface effect' from charging to dissipate. I just charged mine and they were both high 13 VDC, almost 14. The next day they were at 12.6 which is about the most you will ever see using a DMM across a battery with no load.

Almost seems like i have something drawing amps from the battery that i don't know about. Is there a way to check if the battery has a amp draw on it when everything i know about is off??

You could put an ammeter across the battery to see if she's discharging. Check your battery terminals and also, if using wing nuts, THROW THEM AWAY and replace them with nylok nuts. Check all grounds and leads on the OB too.

 

[johnsw]

Just my 2 cents, which might not be worth that much since I'm not familiar with that specific engine.

Like Dale said, measure the charge voltage across the battery terminals with a seperate volt meter while the engine is running. Don't rely on the guage initially, and compare what you get with the guage. If they match and the voltage is low, then you could have a magneto / regulator issue. Cabling and connections could also be a problem. Be sure all connections are tight and corrosion free, and the cabling is the proper guage. If possible, measure the charge voltage at the regulator and compare with the reading you get at the battery. If different, then suspect cabling, connections and anything in between.

Charge voltage should run more than 13 volts, even with some electronics powered on and at idle. You should get about 14 volts running at higher RPM. Motors and pumps can draw a lot of current and could load down the voltage, so be sure none are on when taking the voltage reading.

If you think something is drawing from the battery when it shouldn't, with the engine off use the ammeter function of your multimeter to measure current through the power cable. You have to connect it in series with the power cable, not across the battery. Don't have an ammeter? Then you can use a 12v lamp in series with the power cable. If something is drawing current, the lamp will glow. Dim if current draw is low, bright if its high.

Just an FYI that you might or might not know about: Using a lamp can help locate shorts that blow fuses in electrical systems. Remove the fuse and clip the lamp across the fuse holder. A short in a circuit will cause the lamp to glow brightly, and the lamp will limit the current allowing you to work with the circuit. You can then disconnect things and use the lamp to monitor. When the lamp goes out, you found the circuit with the short.

Electrical problems can be frustrating.

John

 

[warthog5]

To add to what the guy's said. You can test this in the driveway on the muffs.

You want to move the throttle into neutral warm up mode. Have the motor turning 2000RPM.

You should see 14.2V at the battery with a DVM

If not you have a charge problem. The fact that you are showing voltage over 12.6, but just barely would lead me to believe a bad voltage regulator.

BUT!

Like they said. Don't trust that gauge. Check this all out with the DVM, BEFORE you jump to spending money.

You already spent to much.