Is the motor running hot?
It's possible the intake is partially blocked (screen under the plate at the prop) -- more likely if it's a salt water motor, or a river runner (sand). It's somewhat possible to use a modern motor flusher if you take off the rectangular plate above the plate, on the side -- have to cut down the round flusher cup, or buy a square on. But that aside, you can use a hose to get some water in there, maybe using the male end of a quick disconnect -- try that for cleaning out the foot including the intake by the prop (motor off). Similarly, you can flush down from the t.stat housing -- note where the water exits and see if it comes out of the exhaust port on the leg with "vigah."
