Low water flow, and water leaking from around #1 cylinder

[Procraft Bob]

Gentlemen:
Appreciated your advice in the past, and am looking for it again (1994, Mercury 115, 2 stroke, 0G102xxx). Noticed a smaller stream coming from my water pump outlet (weep/pee hole) last year, so I thought I?d replace impeller this year. Engine running fine, but approaches overheat when I have extended idle time (no wake) running. No problem at full throttle. After receiving replacement impeller, I decided to take a last look inside housing before replacement just to insure that was the problem. Hooked up the hose and muffs, and started the engine. OH MY! Much to my chagrin, I see water coming out of the head around sparkplug #1 (top). Still small stream out weep hole, but something isn?t right with water pumping out of head pretty strongly, not just a leak.
I?m mechanically inclined, but no Merc. Tech. Am I off to the repair shop/marina for an expert fix, or is it something I can tackle in my garage? Surely it must be at least a gasket issue, but I guess it could be more than that I?m sure. Parts diagram of engine shows the gasket but lots of stuff to remove to get there. Any advice appreciated. [Viewed a lot of posts with similar problems, but none on point for me.] Engine continues to start and run fine, even with pretty substantial leak, so there must not be any water getting into cylinders. I hope....

 

[RCO]

That motor doesn't have a cylinder head, there is a water jacket cover though. Pretty straight forward job to replace that gasket. Check the cover with a straight edge or glass plate before reassembly.

 

[Texasmark]

At low speeds your engine cooling is regulated by a thermostat. From about mid rpm on up it is bypassed by a popoff valve allowing a larger volume of non temp controlled water through the block. Both are under a cover at the upper left corner of the water jacket plate that is leaking around cylinder #1. So while you have the plate off to install a new gasket, might have a check of your stat and while you are at it, just replace it and the popoff.....if they have never been changed, long overdue with a 1994 engine.