Water in Cylinders!

[Sportdog]

Hi guys, first time poster here and I have a problem. I noticed that my 1997 Mercury 4cy. 2stroke outboard was running hot. I still had a decent stream of water but did notice that it wasn't what it should be. My buddies told me to change the water pump impeller so I got a manual for the motor and the parts and did it. I don't know if I did something wrong or the problem of water in the cylinders already existed but I noticed water coming out from around my spark plugs when it was running. The motor ran fine and did until I started it after the water pump replacement. Well, it still runs ok for the very short period that I ran it. My question is this....Is there something that I did or didn't do that is causing this problem or do you think that it was there already from getting hot? This was my first foray into the world of outboard motor maintenance other than winterizing and it didn't go to well. What do you guys think? Thanks for any replies, much appreciated.