Hi! Before you go to the expense of a logic board, definitely try replacement RAM. Often the memory itself gets water damaged, and simply replacing it brings the computer back to life. I've had many a water damaged MacBook sold to me for $100, only to find that replacing the RAM brought it back to life. That's not always the case, of course, but it happens enough that testing the memory is just about the first thing I do when faced with a "dead" MacBook. Try a single module of known-good RAM, and try it first in one slot with the second slot empty, and then if that doesn't work, try the reverse...this technique lets you know if one or the other slot is damaged.