What a great response. I did:
- The impeller has been replaced so it should be OK.
- Siphoned around 17 gallons of 2 year old gas from the tank.
- Switched to new plugs
- Will use High Octane Gas with a little Boost in it
- This weekend, I'll locate the Sea Foam and insure it's in the tank
If that doesn't clean it up, I'll take it in for the carburetors rebuilt. I would do it myself, but don't have a clue, or know where to get the parts (unless there's a web site).
Thanks to all who gave expert advise. I'll let you know how it goes.
Regards,
Steve