Steam is coming from my dump lines when idling thru no-wake zones and after moderate 4000 rpm runs. I was plumbing the water from the pump, thru an oil cooler, into the motor, using a thermostat system and out thru two dump lines. My headers are T'd off seperatly at the pump. Recently, I used a pickup from the ride plate for the oil cooler and out one of the dump lines and plumbed the cooling water for the motor directly to the thermostat and out the other dump line via a T connection. Yesterday I took her out for a test run and am still getting steam from the engine dump line after shutting the motor off. I have two water temp guages, an elect and mech. Both indicate 160 deg during normal operation and up to 200-220 deg when idling under bridges and after shutting the engine off. Using a 160 deg thermostat; should I try a 140 deg.