Overheated!

[imported_Bluefin]

Hello all, I just recently bought a fishing boat with a 1992 Mercury 50hp 3cyl and while I was trolling the siren went off that indicates overheating. I pulled the hood and let it cool and she fired back up and I was able to get off the lake. Water is coming out of the small hole on the side of the motor but it does not seem to be a good hard stream like I am used to on other motors I've' owned. Is my impeller shot? Please help. Thanks