Hi Jim and welcome to the forum.
racerone makes a good point. You need to put the motor in a bucket that has water deep enough to cover the cavitation plate by a good inch or more. Hopefully you did that.
It sounds as if the previous owner operated in some pretty shallow water and that is where the sand came from. Not all that unusual really. The pump, when it is in good condition, will push that small stuff right on through and out. But, occasionally something like grass, moss or very small twigs or pebbles will get in there and get lodged and will completely block off the tell tale passage.
First off, take the port side cover off so that you can work on the motor. The screws can be a beast to get off and I use an impact driver to get them off easily. Make sure that no one before you has routed the "pee" tube incorrectly so that it gets pinched closed when the side cover is replaced. This happens a lot when the oil filter is changed. I've done it myself more than once. The proper routing for the pee tube is from the nipple on the engine block up through a hole in the "shelf" that sits under the oil filter and then out to the side cover discharge fitting. Make sure you remember to route it this way when you go back together.
Take the hose completely off of the fittings at both ends and verify that the hose and the plastic fitting on the side cover are completely free of debris. Next, you can remove the nipple that is screwed into the engine block and make sure it is unclogged. Then, with the water level in your bucket above the cavitation plate, start and run the engine. Water should pretty much gush out and. if it doesn't, then you definitely need a new pump.
If it were me and I had just purchased the motor, I would want to change out the pump anyway just so that I was secure and confident in what I had there. These are G.R.E.A.T. motors but the easiest way to trash one is to run them hot. On a 2003 model, I would use the COMPLETE water pump kit, not just change the impeller. You get everything you need except the "water grommet" (a half moon shaped seal that goes in front of the pump) and the cost is not that much more than the skimpy impeller kit. I would also replace that rubber "pee" hose as they tend to get hard over time and clog up more easily. I also like to slightly drill out the plastic fitting on the side cover for the pee hose as it seems to get clogged very easily when operating in water that has moss, pebble sand or small twigs.
Also, while your at it, at the very least, take out the thermostat and inspect it. I don't see much sense in taking one out and not replacing it but that's up to you. Just be aware that a stuck thermostat is another way to damage the engine even if it is stuck open. An outboard that operates too cool will deposit unburned gas in the crankcase and could eventually ruin the engine bearings. A fact all car, truck and boat owners should know is that cooling system problems are where 70% of all engine failure begins. I hope this helps.
p.s. I see the rr on your email. Is that for railroad? I'm an old Illinois Central man and was just curious.