2004 90HP Lower Mount Cover Plate

[1stboat-fl]

Hello!
Had a corroded cover plate, found the part online and thought we were just going to change it out. We took the cover plate off the fine a pile of yulk under the plate. What is that? See pic below. I read a few threads -- I came across some thread with the info in "example 1" pic. Which makes since to me. But where is the yulk? Did my part deteriorate into the first picture? Or do I need something more before I put on the cover plate?
Thanks in advance for any information.

 

[racerone]

Must be a salt water motor.-----All a corroded mess.-----Time to see if you canb salvage anything.----Install a new mount and then the cover plate.

 

[1stboat-fl]

Must be a salt water motor.-----All a corroded mess.-----Time to see if you canb salvage anything.----Install a new mount and then the cover plate.

Oh yes, saltwater in the Gulf. My first boat. When I pull the other side it’s just as bad. If I do a side at a time will I be ok with everything staying in place? It’s called a mount... I mean ... is it stable. Forgive my cautiousness of ignorance.