Mower issues

Not sure if this is the best place for this but have a question about I'm hoping someone can answer. I just purchased a used mower not sure how old it is but im guessing mid 90s. I purchased this mower mainly to tackle the weeds on my property so didn't need anything fancy. I knew it needed a new battery so i picked one up today, replaced it, and started mowing. It works well and got a lot done until i ran out of gas or at least that's what I thought. After filling it up and trying to start it I had nothing not even enough to crank it over. After jumping it it ran until i shut it off and then nothing again and now every time to start it I have to jump it. I'm pretty sure the alternator is working but I'm not a hundred percent, whats a way to check for sure? I'm not sure what to look at and unfortunately I don't know what brand the mower is, looked under the seat but the label that was there is no longer there so no model or serial numbers. The engine is a briggs & straton but other than that no idea, the only markings on the machine say 12.5hp 42 inch cut 7 speed-ic. Any ideas or suggestions would be greatly appreciated.

Post a photo. Maybe somebody will recognize it.

You should be able to find engine data. Briggs stamps model, type and code on their engines.

To check whether the alternator is working, check battery voltage before you start the engine and after. A good battery will be around 12.7 volts before start, 13 or more with engine running.

Have the model, type, and code number on the engine as well. Didnt have a hood when i got it.

I would guess it's one of the MTD brands .. possibly a Yard-Man or Yard-Machine , I'm sure one of the dealers on the site would know for sure ... keep us informed ...Boobala

After looking closer I see the Left side PEDAL is not mounted THROUGH the fender assy.
and therefore the top portion bends in-ward instead of out-ward ( similar to older sears mowers) a few more pics would be helpful also ..

According to the numbers on your engine shroud ...( Model = 289707 & type = 0154-01 ( I think) )
your pics aren't very clear... that is a FLATHEAD motor, and this should be your manual for it ..

https://docs.google.com/file/d/0B6NaqjIxWV1ycG8wd0s3Z2Q2X00/edit

However here is the OHV Manual as well, (just in case someone has changed out the shroud )

https://docs.google.com/file/d/0B6NaqjIxWV1ybEN0LWo3azl6OUU/edit

Thank you for that. I metered the battery- not running reads 12.86, running reads 13. When I metered the alternator it was 27-30 so I'm not really sure what's up.

found a wire thats not connected but cant seem to find out where it goes. Its the black wire coming out of that top connector, the other wire goes down and to the engine from what i can see.

I don't see a diode in there anywhere .
Pull the blower housing off and post a photo of the stator.
It should have 2 wires coming off it.
One should have a diode ib the wire to convert the AC into pulsed DC that goes back to charge the battery.
The other wire is AC and goes to the headlights.
The headlamp switch is on the ground side of the globes.
Also a shot of the magnets on the inside of the flywheel would be a help
Briggs have an Alternator Identification chart you can download for free off their web site to help you to identify what you have there.
What has happened is someone has replaced the engine and just chopped the wires to get them to fit which is quite common as the kit B & S used to flog with all the correct connectors is very hard to come by So I have to do the same thing is the looms don't match.