Mercury 25hp EL 1999 loses power and stalls during acceleration

The issue I'm having is once I accelerate past half way I lose power and if I don't back off accelerator the motor will stall. It starts right back up and idles fine and will run fine as long as I don't accelerate past halfway. I have cleaned fuel filter, checked fuel lines, changed spark plugs, and cleaned carb. Still having issues. Any advised would be greatly appreciated. Also I have noticed on my fish finder my battery voltage seems to be rising above what it normally does. By that I mean it usually runs between 12.5 to 14 volts and when these issues started I've seen it as high as 17.5 volts.