300 row crop 6v or 8v

just bought a farmall 300 that has an 8v battery in it. It quit charging so I had gen. rebuilt but needle bounces everywhere. Did these tractors come with 8v or should they be 6v? I have no manual yet

from factory - 6 volt.

They came with 6V I changed mine over to 8V still had cranking problems sometimes hoping it would start changed it over to 12V never have had a problem again.

6volt. The biggest issue is cable size size "O" cables are needed, and the timing set to TDC at engine stopped. Positive ground!
Jim

8v is simply a bandaid to cover up other problems.Draggy starter,too small cables,corrotion,etc will effect crancking.If things are 'up to snuff',6v will start it just fine.

8v is simply a bandaid to cover up other problems.Draggy starter,too small cables,corrotion,etc will effect crancking.If things are 'up to snuff',6v will start it just fine.

8V is a bandaid, convert it to 12V if you are going to work with it, leave it 6V if you want it correct. You will never regret having a 12V working tractor.

AS noted previously, all F300 Row Crops came factory with a 6 volt positive ground electrical system. Some may have been converted over to twelve volt positive ground after the 350's 450's came out, and dealers offered this conversion.
The amp needle jumping is caused by the voltage regulator "buzzing",
I would clean the all wire connections at the genny & voltage regulator shiny bright & coat with di-electric grease before re-assembly,
Then follow these instructions:
http://www.vintagejeepparts.com/PDFs/INSTRUCTIONS FOR INSTALLING VOLTAGE REGULATORS.pdf
If the needle is stilll "jumping" the regulator is still " buzzing" and needs adjustment, remove the regulator cover, file & clean all contact points, then re-set the air gaps:
http://www.42fordgpw.com/voltage.html

Your regulator is different than the ones shown but the contact cleaning & adjustment procdure is the same.

I have an F300 rowcrop & have tried the 8 volt battery. Yes it starts quicker, but you tend to blow light bulbs a little quicker , and fry a lot of points. The trick I have found is bring the wiring harness up to 10 ga wire & above, clean every contact point to bright & shiny, coat with di-electric grease to keep them from re-corroding, (double ought) 00 battery cables with the ends soldered, rebuilt genny, rebuilt starter ( brushes, bearings,bushings, starter drive) adjusted the fan belts, and tuned to where it will start after two or three revolutions. This was a carb & distributor rebuild ( carb kit & pivot weight pins, springs retainers, shaft bushings, echlin brand points, condenser, rotor, new IH distributor cap.
This worked very well until the coil went bad, would get so hot during a parade that you could not lay your hand on it, replaced the coil & life is good again, purrs like a kitten. Don't get me wrong, it took almost two years to get all this accomplished, do what you can when you can, and be wary of some aftermarket replacement parts such as points, you get what you pay for, I went through six aftermarket sets of points & condenser, I found the echlin brand & they are made much better, almost twice the price, but this set has lasted me two years now with no issues ( well as of today anyway).
1. check & adjust fan belt tension
2. clean any & all wire connections to shiny bright
3. clean battery posts & connections
http://www.carkb.com/Uwe/Forum.aspx/gmc/582/voltage-regulator-set-up