18 Volts reading - help?

[jblaiz]

Just came off the water early with a potential (?) concern: I've got an '84 Grady White - 60HP '90 Johnson VRO engine. My CONCERN is while I was out this morning the voltage meter was reading between 17 and 18 volts - I understand there can be a couple volt jump while the motor is running, but I do not recall it jumping this much - 5+ volts: I got off the water in case there is a potential issue here - can anyone let me know if this is an abnormal voltage reading? or within normal running reading??? thanks for any help - HAPPY MEMORIAL DAY to all at Iboats.com forums!

John

 

[JoLin]

Re: 18 Volts reading - help?

Hopefully others here can lead you to the cause, but yes, that's abnormal. A fully charged battery and a correctly operating alternator should yield a reading in the range of 14 volts, plus or minus a little. Looks like you're overcharging, and that'll boil your battery. Make sure you top it up with distilled water before doing anything else.

 

[Boatist]

Re: 18 Volts reading - help?

First thing I would do is check your voltage reading with the key on but before starting. It should read near 12.6 volts if temperature is in the 70 to 80 degree range. If it normal before starting then I would start up on muff and see if it climes right back up. If you have a voltmeter also verify that it also reads the same as your voltage guage at the battery.

18 volts is too high and a 97 Johnson should have a voltage regulator of some type to prevent the voltage from going over 15 volts.

You would be better off to post this in the Johnson Outboard Fourm.

I do not know that motor but the first thing you should do is buy a OEM Service manual. Trust me it will save you time and money. If they move this to the Johnson Forum I am sure someone can help you but the service manual is the best starting place. Likely a wire off or shorted on a defective voltage regulator.

 

[180shabah]

Re: 18 Volts reading - help?

Verify the gauge first.

 

[642mx]

Re: 18 Volts reading - help?

Use a DVOM (digital volt ohm meter) to verify the resting battery voltage and then the running battery voltage. I had a similiar problem, my volt gauge was showing 10 volts while running, but the DVOM showed 14.5 running volts, which means my gauge is not functioning properly and my alternator is fine.