Is my water pump bad?  When I idle there is not a lot of water coming out of the hose and it will overheat when idling.  When I am running, more water comes out but still not a strong stream, but it does not overheat.  If so, is it hard to change out?  I have a 120 Johnson V4, 89 model.

Thanks

When was the water pump impeller replaced? If it's 18 years old, I would stronly recommend you replacing it. I replace mine every three years.

If you can turn a wrench, they are not real hard to change.  getting the screw that hold the shift rod out is about the hardest part to get to.  Then make sure you take the trim tab off, there is a bolt hid under it.  I prefer to trim the motor up when I'm ready to take the last bolt out.  The LU is pretty heavy and it has to be trimed out some to get enough clearance to get it out.