1978 80hp merc

I have been having a problem with my charging system overcharging.
My depth finder on my boat keeps flashing accross the screen high voltage.
The unit is showing 17.8 volts. I thought there was a problem with this humminbird unit . So i took a volt meter placed it on the battery with the motor running, And that also showed 17 volts. I replaced the rectifier.
I still have the same problem. What should i do next.

Re: 1978 80hp merc

hi ....welcome to i boats.....hows about we get this moved to where you can get some answers to your questions

Re: 1978 80hp merc

http://forums.iboats.com/showthread.php?t=250877

Re: 1978 80hp merc

cptfisherman said:

I have been having a problem with my charging system overcharging.
My depth finder on my boat keeps flashing accross the screen high voltage.
The unit is showing 17.8 volts. I thought there was a problem with this humminbird unit . So i took a volt meter placed it on the battery with the motor running, And that also showed 17 volts. I replaced the rectifier.
I still have the same problem. What should i do next.

Click to expand...

That is a 16 amp, or maybe a 9 amp system. Either way, it probably doesn't have a voltage regulator on it, but relies on the battery to hold down the voltage. If it does have a regulator on it, it's an additional module with 1 or 2 wires going to the rectifier.

It works OK, but you have to pay attention to the battery as it will use up the water in the battery making hydrogen and oxygen gasses. The battery life is limited somewhat anyway by overcharging, but usually they will last till the battery warranty expires. (go figure)

Check your battery. You'll probably find it low on water. Top it off with distilled water, and if the voltage doesn't go down, you'll have to replace the battery with a new one. That's the short term fix, and probably battery maintenance is the long term fix.

The rectifier you replaced was working perfectly. Keep it for a spare.

hope it helps
John