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Took out our new (to us) Sakonnet with the aforementioned motor and am curious what voltage should I expect - I understand that too low and battery may not be charging - too high and it would be bad for battery.
TIA
Wayne
A battery at 100% full charge is 12.6 standing voltage (not being charged). I have found that analog style volt meters used in boats typically are up to 1/2 volt off in actual reading. My depth finder seems to be the most accurate for reading voltage when compared to a digital volt/ohms meter. For your engine, which I have one on one of my boats it typically reads 12.9 volts at idle and 13.9-14.2 volts above 3000 rpm's. This is charging voltage, not the actual battery voltage. As I mentioned, the actual battery voltage is measured at rest, accessories off and standing for at least for 1 hour after being charged. I prefer to have them sit overnight after being charged to measure their actual state of condition. One thing I've learned about batteries, when you are buying a replacement make sure you get newest date code/sticker that says when it was manufactured. Ask to have the battery voltage measured and you want to see 12.5-12.6 volts in a new battery. If the battery shows a date sticker over 6 months old, don't buy that battery because as batteries sit, they lose voltage and a lead acid battery sitting for months partially discharged will ruin the battery. I learned this the hard way.
Thanks fitz for that comprehensive reply. Your reply was just what I was looking for.
My concern is that our new Garmin fish finder was reading 14.5 volts while we were cruising (we don't have a working tach) - I'm a little concerned that this reading may be too high. My ROT for car alternators has always been 13-14.2 volts during driving.
BTW- i am using a relatively new car battery, not a deep cycle or anything special, in the boat - it was handy.
Do you think 14.5 should be of concern?
heimtun wrote:
Thanks fitz for that comprehensive reply. Your reply was just what I was looking for.
My concern is that our new Garmin fish finder was reading 14.5 volts while we were cruising (we don't have a working tach) - I'm a little concerned that this reading may be too high. My ROT for car alternators has always been 13-14.2 volts during driving.
BTW- i am using a relatively new car battery, not a deep cycle or anything special, in the boat - it was handy.
Do you think 14.5 should be of concern?
Not a major concern, but I would consider it at the high limit of charging voltage, my 60 Merc will occasionally hit 14.5 volts at high RPMs. My twin 115 Mercs on my '73 22-2 Aquasport also run about the same voltage at high speed and settle back down to 12.9-13.2V at idle so there is consistency even in different engines and applications. Check your battery water level after a couple of trips to make sure its above the plates. If your not using a lot of water in the batteries from being overcharged consider everything OK.
Remember that many older motors had no regulation in the charging circuit, so it was common to see voltages well above what would be considered normal in a car, for example. If memory serves, my old 1989 Johnson 70 would show north of 16V at high speed, once the battery was fully charged. It only put out 6 watts total, so that did no harm to the battery, but I can well imagine newer electronics might not be happy. I did buy an external regulator before installing a GPS, but then ended up replacing the motor before I ever used it.
So in general, I would not sweat the readings you're seeing, but you might want to check the motor specs to be on the safe side.
tedious wrote:
Remember that many older motors had no regulation in the charging circuit, so it was common to see voltages well above what would be considered normal in a car, for example. If memory serves, my old 1989 Johnson 70 would show north of 16V at high speed, once the battery was fully charged. It only put out 6 watts total, so that did no harm to the battery, but I can well imagine newer electronics might not be happy. I did buy an external regulator before installing a GPS, but then ended up replacing the motor before I ever used it.
So in general, I would not sweat the readings you're seeing, but you might want to check the motor specs to be on the safe side.
In that case, I'd echo the previous poster - the voltage is a little high; not a major concern at 16A, but check the water level from time to time just to be on safe side.
