I have a 84 Mercury 9.9 and over the weekend it quit "peeing" on me. I replaced the water pump in it about 3 years ago. My question is could it possibly be clogged by debris. I visually inspected the intake and did not see anything.

Could flushing the motor help? How does that work, I see a flush plug but it is fairly small....about a half inch in diameter. Do I need some type of attachment?

Good thing is i did not run the motor long at all...the next day I started it to trailer it and it started peeing again....kinda had me confused.

Any suggestions

does that motor have a thermostat?

No