I have a 89 mercury v200 and am in the process of replacing all of the check valves in the oil injection system. I noticed on the one that comes from the crankcase to pressurize the system, it isn't completely air tight. As a matter of fact, i have twins and both crankcase check valves leak a little on the backflow. Is this normal? They are both brand new, out of the package quicksilver parts. Any help would be appreciated.