Re: I'll give you a shiny penny if
And I'll give you a penny if you can produce a 1982 Sea King made by Johnson. What do you REALLY have?
If it really is a 1982 Johnson 25hp, the water intake is a screen on the leading edge of the exhaust outlet, just aft of the prop. Those holes above the cavitation plate are to let water in when running in reverse. Putting water in them with a hose will only run out the screen previously mentioned.
There was a flushing attachment made many moons ago, but they are very rare these days. It was called a Tempo Flushette. There were several motor-specific models.