looking at purchasing a 1999 mercury 200 efi. any problems or concerns I may be getting into or is it a solid motor? thank you for answers

Make sure all 6 injectors or whatever they are called in the ECU module are functioning properly. That is the issue I had dealt with.

good engine if taken care of. run some injector cleaner thru it often is all I do with my 95 200 xri/efi.

Fuel sucking hogs, but seem to run a long time. (If taken care of)

my 96 only uses a lot o gas when it is running, gets me to the area , then I shut it off,then put down the trolling motor

My 2000 merc is still running good, on my ol p2 . That said i rarely run it w o t. Had it for 8yrs.

i've got a 1998. great motor and always reliable. i don't believe they can run hours on that year model.

I would not hesitate to buy it if you have it checked out by a knowledgeable mechanic. a few things:

1. Bypass the oil injection and mix your own gas (if not already done).
2. get it serviced and they should/can test each of the injectors - if one fails, then you don't get oil to the cylinder = bad news.
3. run Mercury quickclean treatment with every tank.
4. Voltage regulators = these have known issues and can fail or catch fire. keep an eye on your tach and if erratic then replace. probably $400 to $500 to get new ones.

and of course - have the compression checked whichever brand motor you decide to go with.