I've had this happen as well. It was a big clump of weeds clogging up the intake grate. Hopped off, cleaned them out and everything was good again.This happened to me. Was cruising along normally, and all of a sudden loud vibration and high RPMS. thought it had to be the wear ring. Limped for like ten minutes, then kept it cruising at under 5000 rpms while dealing with the heavy vibration and it cleared after maybe 15 minutes. Gone. I have ordered a new wear ring and plan on replacing, hasn't been back in the water since. Its been 4-5 days.
I think the ring is coming in on monday, so I may try my luck with it this weekend on the water and see how it holds up.
As far as how much it should cost at the dealer...
Honestly if they charge you more than 1 hour labor they are completely out of the ball park on price. Truthfully, the wear ring on a Spark (especially one without IBR) is so easy to do that even someone with virtually no tech savvy could do one.
You can buy a spare wear ring at SBT for about $52.45 plus shipping.
I bought one of the SBT wear rings as my spare for long trips. It feels sturdy enough and I fully expect to be able to change it at the side of the lake if necessary.
Instructions on changing the wear ring can be found at: