Rebuilding yamaha 40 hp outboard

My pressure check reads about 85 per cylynder. Friends say yamaha 40 are work horses. But my pressures should be higher 100+ is good. Motor still runs but is a 97 one owner.Should I rebuild or go new. Really can,t afford new right now but don't want to throw away money on prolonging the inevadiable. How many years should I expect a rebuild to get me, and the average cost.by a registered dealer.