I have a Yanmar 2GM and have installed a connection to flush the raw water cooling circuit with a hose before shutting it down. The fitting is installed between the thru hull and the strainer. While the motor is running, I turn the hose on about a quarter turn and then close the raw water intake. I watch the exhaust, and the coolant exiting the boat looks normal. Can I do any damage by having too much pressure in the fresh water hose? I assume the thermostat will prevent this from happening. Is this correct? I tried flushing the motor with the top of the strainer off, but got an air pocket in the system the next time I started the motor. I could also turn the pressure in the hose up with the intake open allowing any excess pressure to exit through the intake. Thoughts?