I have a ’59 Flying Scott 60 hp that is over heating. I looked at the water pump impeller and it looks good. I did not see any other issues when I pulled the lower unit. It will run 2-3 minutes before the temp light comes on. There is a solid stream of water coming out of the weep hole on the left side under the engine. I have been running it in a test tank. Any ideas on what else might be the problem?