Just purchased a 1989 Hurricane with a Mercury 150 which is a 1993. it has a oil injection tank on top of the motor and also a couple gallon tank under a compt. previous owner says oil injection works . it also has a 17 gallon fuel tank. Is there any way to check oil injection and should both tanks be filled. I believe the tank on top of the motor leaks when tilted up. Cap is a drain plug. Which way to go. do not want to ruin a good engine.