Golf cart acceleration issues

I inherited a 1997 electric ezgo txt cart. I am having issues with acceleration. I can feel the cart trying to move, but it will act as if it is in a limp mode. This happens in fwd and reverse. Occasionally, the power will kick in and the cart will accelerate just fine. It will sometimes slow down again after about 15 seconds of moving. The batteries are just over a year old, but the cart has not been operated much this year. I used a multimeter on the batteries after a complete charge. All batteries were showing 6.62. Not great, but I feel it should be enough to operate normally. Thanks for any advice.