So, I took the boat out on the bayou this afternoon for a quick run and to try some fly fishing.

I get out and notice the volt meter is high...as in 15, almost 16 volts (runs around 12 to 13 WOT usually)

Being rather surprised, I slow down and turn off the engine. I turned the power on (engine off) to see what the gauge would read...12 volts.
So, I'm thinking it's the alternator.

Then I turn the engine back on and drive a short ways and the gauge jumped back to around 15 volts. I turned on and off all switches on the boat and nothing changed.

I finally, tried the tilt which caused the volt meter to drop back down to 12. After adjusting the motor up or down, the gauge would drop to 12 and then work it's way back up to 15-15 volts.

What do y'all think is the issue?

Edit: The engine is a 2006 90 hp Yamaha two stroke

This post was edited on 5/5/13 at 6:50 pm

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Posted by Hammertime

Will trade dowsing rod for titties

Member since Jan 2012

43030 posts

Posted on 5/5/13 at 6:55 pm to stewie

Bad gauge or wiring for the gauge

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Posted by LSUwag

Florida man

Member since Jan 2007

17319 posts

Posted on 5/5/13 at 7:02 pm to stewie

I don't know about a boat alternator but in an automotive alternator, when a diode goes out they over charge and cook themselves.

Could be the same thing going on here.

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Posted by bapple

Capital City

Member since Oct 2010

11913 posts

Posted on 5/5/13 at 7:02 pm to stewie

quote:
I finally, tried the tilt which caused the volt meter to drop back down to 12. After adjusting the motor up or down, the gauge would drop to 12 and then work it's way back up to 15-15 volts.

Anytime a load is put on your power supply, there will be a voltage drop, especially something that pulls as much current as adjusting the tilt.

I would check to make sure none of your electronics would be affected by the slightly higher voltage. If not, just let the alternator do its thing.

If you put a volt meter on some of the outlets in your house, I doubt you would get an exact 120V anywhere. There are small fluctuations that do not make a huge difference.

Hammer could be right in that your meter could be bad, but I doubt it since you say the voltage returns to 12 after the motor is off.

PS I'm about to graduate in electrical engineering, so while I'm not expert, I feel I know a couple of things.