Kawasaki Jet Ski i have a 750ss and my oil pump failed could i just mix the oil and gas and leave the pump hooked up?

I don't think it would hurt anything if you did that, but just to be safe I would block it off. They make an oil pump block-off plate kit that you should install in place of the oil pump. It's an easy job.. just remove the two bolts that are holding the oil pump on and the block-off plate just bolts right on where the pump was. Then you can start running the gas and oil premixed in the gas tank (40:1).