I would buy a Mercury or Mariner (same company) 150 and never look back. My 1988 Mariner 150 has run like a watch since I bought it new and has only required normal maintenance. I do change the water pump every three years.
Outboard Marine Corp. (Johnson/Enivrude) went bankrupt in the late 90's....the last products were built under duress. Then parts for repairs became a real problem, because Bombardier did not buy the right to parts for past motors. So the '99 you're asking about fits the "unknown" category.
Nothing wrong with the same year models of Mercury/Mariner...they are exactly the same product except for the part numbers of the paint and the decals. The Mariner has been out of new production since 1999 (just Mercury worldwide now). That was a marketing decision, not a product decision.... but the Merc's are stronger than ever.
If I was buying anything from the late 90's on, in a mid-to-large hp model, I'd consider Yamaha, Honda, and Mercury 4-strokes, in that order. If you want the best 2-stroke avaiable, consider the Mercury Opti-Max.....none better. Incidentally, I'm a retired Mercury dealer.
Down here on the TX coast; inshore saltwater guides run Yamaha's if they can afford them, the others run Mercs. I ran a Merc since 1988 with no major problems. Lower units built like a tank. I ran my flats boat for 4 years with a Merc before I sold the rig in 2000. No problems whatsoever.
I too was an OMC. guy, thought Mercury was the only motor to run. All were strong, and performed exceptionally well except for cold mornigs. I have since switched to a Yamaha HPDI. it is quieter than a Mercury, and comes out of the hole better and performs better at mid range as well.(better throttle response). My two cents worth. hope it helps.