[sluggo]

Look at the new one and see that it's threaded on both ends.  Then turn it leftie loosie to remove and rightie tightie to install. 
Capt. George

thanks, I know that, but if you look at the pic, the forward fitting is almost square (the one aft I could easily see and it was just a hose fitting).  So I guess I can just put my pliers on the square fitting to hold it tight, and start left loosie.  thanks again.

As a follow up. Thanks I got it put a pair of channel locks on the square fitting and turned the filter loose. No problem!! Took all of 10 minutes.  

Just changed mine as well!  Thanks for the post.  Fortunately was able to unthread mine by hand.  Tough spot in the boat though!.

FWIW by changing this, it really helped with the smell on the boat, not that there was very much, but you can tell a difference