Re: Mercury Outboard no pee hole discharge
Not sure, but I believe the "pee" hole discharge system, was partially meant to allow the water to fill an area which the impeller system wasn't reaching, or water to be routed to an area where there could be a natural "airlock".
The tapped hole on the cooling jacket is usually in a spot that seems to be in a most remote place or in a place that looks like it could be an airlock area.
This is just my thinking, because it makes sense to relieve any areas that may have caused hot spots in the past, rather then to redesign the same block.
Who needs an extra flow indicator (pee hole) if you can tell tat the circulation is ok by checking the exhaust flow? well, those who had a problem with airlocks.
As for the problem you describe of not seeing it work, (which you have fixed at this point,) I would start with the simplest remedy first, and that would be the cleaning of the hose and fittings from the water jacket to the last place where the water should come out.
If your exhaust produces water, your impeller is producing water flow, but how much is anyones guess.
I have no idea how much pressure the impeller system should produce, but can imagine that it should be at least a few pounds to allow flow though the system.
Hope that gives a bit of peace, take care,
John.