That motor has a thermostat controlled recirculating cooling system. Water from the pump circulates through the powerhead and is then presented to the thermostat. If the ‘stat says it is too cool, the water pushes through the relief valve next to the ‘stat valve and returns to the water pump for recirculation. When the ‘stat decides it is warm enough it opens the discharge valve and the water is discharged and replaced with cool lake water. This is not an either-or thing. The ‘stat is constantly sampling the water and opening or closing as necessary to maintain desired temperature. A slot in the discharge valve allows a bit of water to discharge even if closed. This is necessary in order to cool the exhaust and provide a visual discharge out the exhaust relief hole.
There is a convenient place to access the water if you insist on seeing it pee. The port is blanked off from bygone days when they had a hot water choke. Drill & tap 1/8 NPT and screw in your hose fitting.
