I have bought a 1971, 9.5hp. I wanted to change the gear case oil. I took both screws out to drain it. Nothing. It looked like a thick grease was inside, no oil. Is this because there is a leak and someone put grease inside so it would not leak? The motor has run for about eight hours, that I know of, in this condition. I need to know what would be the best thing for me to do in this situation. The motor starts and runs great. What would be the best way to clean it out. Thanks for your time.