I have had an issue with voltage on the boat, and I hoping I could get some suggestions here.
Breakdown:
One batteryÂ…new
On board battery charger: new
Alternator: swapped out, but not new.
At the beginning of the summer the voltage on the boat would only read 12.8, this was the same started or not started, and often times was more like 11.8. I took the alternator off, and tired to have it tested but most places couldnÂ’t figure out how to test itÂ…and the only place that kinda did, said yeah, the output voltage was low. I happened to have another alternator lying around so I figured I would try it out before I purchased a new one. The wires were slightly different, but I think I got it connected up the same. When I first put the new alternator on, and with a full battery charge the voltage read 14.8-15.1 while the boat was running and 12.6 while not running. I thought the voltage was a little high, but some friends suggested that it might take awhile to regulate if the voltage regulator is externalÂ….so I said fine, and left it for a few weeks. Over these few weeksÂ…this is what I have noticed:
When the battery has a full charge, the voltage is 12.6 when not running and in the high 14Â’s when running. If I play the stereo for a couple of hours and run the battery down, the voltage will read low when not runningÂ…letÂ’s say as low as 10V and then when running it will only read maybe high 12Â’s. NowÂ…what I donÂ’t understand isÂ…shouldnÂ’t the voltage read the same when the boat is running? ShouldnÂ’t it read always around 13.8ish?
Thanks for any suggestions! I was thinking about just replacing the alternator with a new single wire alternator just to eliminate and chance of a faulty alternator.
BTWÂ….this is the first year I have owned this boat, so I canÂ’t go on past history. It is a 1988, 454 mercrusier.
Sounds normal to me with the second alt. If the battery is dead without it running it is going to read low. Running it down to 10v is really hard on you battery. I'm surprised it will start with the battery that low. Once you start it the voltage will slowly come up with the alt. Remember an alt is not designed to charge a battery just maintain it.
Sounds normal to me with the second alt. If the battery is dead without it running it is going to read low. Running it down to 10v is really hard on you battery. I'm surprised it will start with the battery that low. Once you start it the voltage will slowly come up with the alt. Remember an alt is not designed to charge a battery just maintain it.
I don't normally run it that low...I was just wanted to see how long the stereo could run before it was too low to start. I still haven't found what too low is. I don't use the alternator to charge the battery...that's what the on board charger is for. The battery is a opmita blue top 31 series...it's designed for deep cycle.
Isn't 15V kinda high? and it's not only the analog gauge I getting that reading from, I get the same on the gauge as well as my Lowarance GPS unit.
thanks.
15 is high. Mine runs around 14.4 when it is charged up at cruising speed.
Yes you have a deep cycle battery, but 10V is WAY too low. 10.5 is concidered a dead battery. Even if your engine is starting, having that low of a voltage is brutal on your starter motor. try to keep it above 10.5-11.0 as a MINIMUM. Any lower, get that charger on it, your battery life will be greatly increased. You may want to have the condition of the battery checked. If it is starting to go, it may not be loading your alternator properly.
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