I run the 14.5/22.5 Skat Trak which work great in these boats. I'd call the guys at Group K and see if they have a pair in stock. They still list them in their closeout section. groupk.com/index.php/group-k-closeout-impellers/

That would just depend on how bad the wobble is. I have a couple of spare driveshafts on the shelf and went out to check them out of curiosity. Neither had any wobble that I could tell. I did find a spec on driveshaft deflection in the shop manual. With the shaft on v-blocks there should be no more than .020" deflection measured with a dial indicator at the center of the shaft. Part numbers for the driveshafts are 272000073 or 204120064 if you need a replacement.

Removing the oil system and going premix was one of the first things I did. That was 20 yrs ago so no video. If you go to the Seadoo FB pages it seems like everyone recommends leaving the oil system on there and just doing maintenance on it so it doesn't fail. The boat will use more oil premix and smoke more but I still prefer it that way. I've got some work to do on the Speedster this week so I will take some video on what needs done to remove the oil injection. It is a little more complicated than most skis because you still have to keep oil in the rotary valve section of the case. Leaks in the core plugs are common since they rot out from the inside with age. Some guys get by with JB weld but I always take the pipe off and TIG weld it. That would be my recommendation since a used pipe could have the same issue. If you rebuild the carbs use only genuine Mikuni parts. Some of the aftermarket carb parts aren't very good. Better impellers and the older style driveshaft seals were a definite improvement on mine. Other than that I would just enjoy the boat since they are a lot of fun. Thanks for subscribing!

Anything that says marine grease since it handles water better. I'm not particular on the brand.