The Mariners confirmed the signings on Thursday with Powell coming via Wellington and Sydney FC on a two-season deal, while Appiah returns to the club he won the National Youth League (NYL) with back in 2011.

Powell secured a release from the Phoenix earlier this month to facilitate a move back to NSW to be closer to his family and will now join last year's wooden spooners in Gosford.

The 25 year-old has scored 12 goals in 42 career A-League appearances, including a four-goal haul against Western Sydney Wanderers last season that included the second-fastest hat-trick in A-League history.

"Blake is a hard worker; has great pace and makes smart forward runs," Mariners coach Tony Walmsley said.

"He has proved himself to be a goal scorer at both Sydney FC and Wellington Phoenix and gives us a point of difference as a second striker or number 10.

"When we heard he had returned to NSW for family reasons and had been released by Wellington it made sense to make an approach and I'm delighted to be able to add him to our attacking options for the next two seasons."

Appiah, 24, returns to the club from the Phoenix, and the Western Sydney foundation player is looking to get his career back on track.

"My goals for this season are to do well in pre-season, earn that chance, cement a spot in the starting XI and finally score some A-League goals," Appiah said.

Appiah was previously recruited by the Mariners in 2011 as a 19 year-old, where won the NYL in 2011-2012, playing alongside the likes of current Australia star Tom Rogic, and Anthony Caceres, Mitch Duke and Bernie Ibini.