I've got two 240s each still with their original water pumps. The 89 has only done 140,000 miles, the 93 has done 360,000 miles.
The 93 has a small hole on top for applying a few drops of lubricating oil to the spindle once in a while. The 89 didn't have that, but in a recent check I found the pump was getting a bit stiff. I drilled a hole in the same corresponding place as in the other one, and after a few shots of oil it freed up.
I've never had any difficulty making a seal. You have to remember that the pump slides upwards to compress the top seal, so you don't want a fast-setting cement on the paper gasket or you will rip it as you slide the pump.

The belt length is very critical. Half an inch difference in length puts the alternator too close, or off the adjustment scale.

You're funny. Volvo B230 water pumps are better than they have been in the past but for the most part they crap. They stock the pump gaskets seperately because people screw up the installation the first time around, usually at the O ring that sells the by-pass pipe, and they have to take it back apart and re-do it. More often than not you will trash the paper gasket doing so and now you need another gasket for your new pump. I've been doing this crap for 20+ years now and every once in a blue moon I too will screw up a pump install, I tend to miss a teeny tiny piece of gasket somewhere and it will leak under pressure and I get to do it all over again. I cannot remember the last time it happened but you can rest assured that there are a couple of complete B230 pump gasket sets on the wall in my shop. Those pumps were so bad about leaking that while they were under warranty Volvo Cars actually sent out a bulletin that said you had to count the DPM's or drops per minute and only replace the pumps that had a drip rate in excess of 10 DPMs. Hey, I can't make this crap up, too funny huh? At any rate the new pumps tend to work better than the old ones.

Your sparking problem, what kind of belt(s) are you running? Is it the correct factory Volvo belt or a Conti of the correct dimension? If you are running somekind of wildcat BS belt that is too short it will allow the nut for the tensioner to come into contact with the water pump pulley. Your thoughts about a blown out pump bearing are not unfounded either. I have seen pump bearings so blown out that the allowed the pulley to lean over far enough to spark.
Your black crud sounds like black RTV more than anything and it will not cause the pump to sit out too far and even if it did it would cause the pulley to sit out further too which would space it away from the cause of the grinding and not closer.
My money is on the alternator belt set being too short.

Good luck,
Mark

Oooooops, double posted.

Mark

DOn't know about the pump bearing but I have bought and used gaskets and seals for the WP in the past. I like to pirate parts so new gaskets come in handy and I replaced the top seal when I did the head