Re: 1969 merc 40 4hp not peeing
Been a long time since I had the single cylinder Merc. Think mine was a 4.5 hp. To inspect for a pee source, remove the cowl and look around the water jacket; top, both sides, and rear. There will be a plug with a small (1/4-5/16") hose attached that routes over to and protrudes through the cowl, (usually starboard side of the engine) and allows water jacket water to exit where it is visable to the operator.
Dirt dobbers and the like love to plug this hole up in the summer. A piece of small wire, inserted and rotated while the engine is running works for me to clean it out.
If I understand your post in that you found something like I described, removed a (different) plug on the engines water jacket, and was able to force garden hose water through the hose and out of the plug hole in the water jacket then the pee hole is obviously not clogged.
What you have done was to verify that your water pump was not pumping water to your engine and that needs your immediate attention. For you to get NO water from that hole with the engine running in a tank (with the water level well up on the mid section....bottom of clamp bracket is a good height) or on muffs with adequate water supply, you have a bigger problem of a clog (per a critter) or a water pump/routing hose issue.
Mark
