Have a 270 mercury sterndrive. I have bought the boat, but have not drained the foot since i got it. Made shre it was full. When i drained it, it was motor oil in the foot. About 2.5 quarts. Is this correct. I cannot find in my manual its on pdf file. It just says a G5 type. Anybody know what is the correct lubricant. If the motor oil is wrong, has any damadge been done. Thanks.