Wear ring?
It can only be a couple things. If your sure your shaft splines are not stripped out and the shaft is turning while the engine is running, then it sounds like your wearing ring has folded in or your pump is cavitating from sucking are in from where your shaft or steering cable pass through the hull. But it sounds like your pump to me.
You have a wearing ring that is inserted into the pump casing so that over the years, the sand, etc... you pick up doesn't eat through your pump casing. It's also coated with a hard rubber that makes it long lasting. The impellor blades have a close tolerance to this wearing ring. When it gives way, the suction of the impellor will fold it in, blocking almost all the pumps discharge. I know from experience, it happened to me this past summer. I have a 1997 model 787. I've looked at your pump in the manual section and it looks just like mine. The rebuild on the pump is really pretty simple. Our premium members have access to all the shop manuals and expert advise from the moderators and administrators.
I can't really help you if you don't have access to the manuals because you'll have to refer to drawings, etc.... outside of advice from us. I can take the pump out in less than an hour. There is only one special tool you need to get to remove the impellor and it cost less than $20. I also decided to replace my impellor while I had it apart. I found a refurbished impellor guaranteed to meet OEM specs for $25 with a core trade in. If your splines are stipped, it's not considered a refurbishable core and you will have to pay full price, which will run you around $200.
All said and done, my pump rebuild was about $200. I can only imagine how much it would cost if I took it to the shop.
When replacing the bearings, you have to have another tool called a depth gage, but I made my own depth gage by a 2 dollar fix from my local auto parts store and you don't have to have a press to press out the bearings if you have a mechanincs tool box with an assorted set of deep well sockets.
Let me know what you decide and if you decide to take it out, I'd like to know how you fare?......
