Everytime I cross a good sized wake my '88 Mercury 135 gives me the beep-beep-beep of the oil warning system. I replaced the cap on the engine mounted oil reservoir and blew out the oil lines with an air compressor. The engine reservoir stays fairly full and the motor smokes plenty on startup. Beeping stops as soon as you hit flat water or light chop. I get maybe 4 or 5 beeps and it stops. Any thoughts?