looking at getting a boat with this on it.... any known concerns I should be aware of?

OMC had problems with the FICHT engine though I think it was the mid 90's models that were troublesome.

Way2slow can probably answer your question better.

The early 92 150's are some of the strongest 150 made. Johnson acutally was going over the 10% max hp until Mercury, wondering why those 150's were running as strong as their 200's and had some tested and filed suit.

Problem free, there is no such motor. The 60 degree blocks do have a problem with more than a few of the blocks cracking where the reg/rec. If not detected if it happens, it can blow the motor.