Long shutter question -p510

Morning everyone!

I recently purchased a p510 and am starting to experiment and learn.  One type of photo that keeps drawing my attention is the slow shutter water pictures.  So I've been sitting in my apartment playing with the shutter speed with the camera sitting on table.   Switching between 1-8 seconds my goal was to get the tv "blurry/silky" While keeping everything else crystal clear.

My question is - every photo over 1 second is over exposed and washed out with brightness. The exposure correction is not available in manual mode (which is the only way to go longer than 1second) and I'm not sure how to correct this. Ian's ideas what I can change to darken the picture?

thanks in advance!