1980s Mariner 9.9M - Telltale Hole Help

I have a 1980s-ish Mariner 9.9M outboard, serial number 682-339381, that was dropped off for free (attached to a boat). It runs, but it didn't appear to pump water, as the guy who dropped it off said.

It hadn't been ran in at least two years, either, but after tearing the water pump apart and taking a quick look at it, it didn't look too bad. Of course, I ordered a new water pump kit anyway, but everything was in one piece.

There wasn't a drop of water coming out of the tell tale hole when it ran in a bucket of water, so I checked the hose that comes out of the powerhead and through the lower cowling. When I put some water into the intake from a garden hose, water came out of that hose just fine, so I checked the flange that it was connected to on the lower cowling. Sure enough, absolutely nothing was going through it, so I took the powerhead off to check that. It was clearly full of salt, so I soaked it in CLR and a concoction of chemicals to try and clear the blockage, to no avail.

The only progress I've made is a second hole that I accidentally poked through the driveshaft housing with a screwdriver while I was attempting to scrape some of the salt out, right beside the blockage. However, there's a tube going from the tell tale hole upwards that is totally clear. What the heck is the purpose of all these holes???

This is the first outboard I've ever really worked on, so is there something I'm getting wrong here? Is water even supposed to get through that tiny passage, or is it just there to block the other end of the water hose off??? I've ordered all the gaskets that I need to put this thing back together, so I'd like to know what I need to do next before doing so.

Are you sure the thermostat opened? Water doesn't come out until the t-stat opens.

Jeff

I'm definitely not sure that the thermostat opened. I tore it apart a couple weeks ago and it was completely full of sand so I soaked it in vinegar for a few days to clear it out, then I tested it in a pot of hot water and it seemed to open just fine. Even if the thermostat did open, though, there still probably wouldn't have been any way to know.

How can I safely drill out that hole without accidentally drilling through the driveshaft housing? That passage seems so tiny, that's what's confused me the most. I've already accidentally poked a hole in it that I'll probably have to JB-weld shut.

That pee-hole is not controlled by the thermostat as that is a yamaha built motor. I would try a garden hose to push through the water passages. But if the aluminum is thin enough to push through with a screw driver you have bigger problems.

Here are some more pictures of it, if it helps at all.

Can anybody help me out? I've pretty much just been sitting on this for a month now, I don't want to put it back together until I'm sure that the water pump and the tell tale will work.

You have two options: Drill/ poke with a wire to get that hole open, or drill and tap the block somewhere to create another tell tale.

Jeff

About how wide is the hole supposed to be? The passage that it seems to go through seems awfully thin. Just to be clear, I've attached an image showing what I'm talking about. Whatever's stuck in this passage is almost as hard as the metal around it, so it'll definitely need to be drilled out.