It starts up and will idle fine, but when I give it gas to pull up the rider it just quits and goes to idle. I turned off the boat started it up again with the radio off and it worked fine for a while. Then I was pulling someone who didn't want the wake as big so when I was pulling them I started emptying the ballast and it died again right when I flipped the switches. I have two optima batteries and both were on the volts were at about 10 which is a bit low. My only guess is that it's the alternator, but I don't know why that would die when it's only the second time I've used it this summer. Any help would be great.