40 hp Mercury Mariner- Rebuild or Junk?

Question

Thinking about having my 40 HP, 2 stroke Mercury Mariner rebuilt since it is at least 15 years old and has sat, unmaintained for 2 years (bad back injury on my part). This motor is used almost exclusively in saltwater. Anyone know approximately what it will cost since I'm not sure if I'm going to go that route or do you think I should scrap it and go with newer or brand new motor?