2003 F90 Voltage problems

[newdeal]

I just bought a used boat about two weeks ago. It has a 2003 F90 on it. The motor runs well, but I have noticed a voltage issue. When I first got the boat there was no trouble, voltage was just over 14 when running according to the gauge, and to my fish finder which reports voltage also. The other day I was running it and I noticed it was saying 13.6volts while I was driving the boat (5000rpm or so). Today when I was driving it again I noticed it is now in the 11.6 volt range. I have been driving it quite a bit, put around 5 hours on it in the last two weeks. If I rev the motor, the voltage does climb VERY slowly. At idle the voltage starts dropping slowly. I am going to go through some trouble shooting but I am not sure if this is a battery issue or if its a regulator/rectifier issue. I don't think its a alternator issue because when I am revving the voltage does go up a little, just not much.

 

[Grandad]

Dashboard voltage gauges are often not the most reliable way to properly read voltage accurately. I say this because most times the voltmeter is simply connected in parallel with the main feed for misc accessories. Unless you run separate positive and negative wires from your voltmeter directly back to your battery, you're only reading what voltage remains available at the dashboard after other accessories have contributed to voltage drop as current is collectively used. Watching such a gauge can lead to some paranoia. If you're not noticing slow cranking, there may be no problem at all. Your battery's performance over say 5 years or so will gradually deteriorate and it will also develop some internal resistance, but unless your battery is more than 5 years old, it's probably still good. Charging systems often don't offer much at idle and as you've noted, the voltage will rise to a certain point with RPM. - Grandad

 

[newdeal]

It was the voltage regulator. I took it off and the under side was all charred. Got an aftermarket one off ebay for $100 (yamaha charges 300) and put it on and the problem is resolved. The aftermarket also has a bigger heating hopefully that helps

 

[Grandad]

Hi newdeal. Glad you found and fixed the problem. It's always good to hear how things were resolved. I hope my dissertation above didn't lead you off into the weeds. - Grandad

 

[99yam40]

It was the voltage regulator. I took it off and the under side was all charred. Got an aftermarket one off ebay for $100 (yamaha charges 300) and put it on and the problem is resolved. The aftermarket also has a bigger heating hopefully that helps

not sure what a heating is , but the R&R should not have a heating

Look for bad connections that can cause R&R to fail

 

[newdeal]

sorry it was auto correct. It was supposed to say bigger heat sink