When I turn the motor over manually by the flywheel with the motor in gear, the prop turns with no weird noises. However, then I pulled the upper and lower drain plugs on the lower unit today, absolutely nothing came out. Not really surprised, but I am concerned. Should I flush out the housing with something first to look for metal shavings/Chips or just refill it to find the leak? If it should be flushed first, should I just use the lubricant or something else. Little concerned about possible sludge buildup to.