I'm assuming this is a 1200 FITCH engine in either a Virage or a Genesis?
That engine isn't firing one of it's cylinders.
1) could be a bad spark. (From the hall sensors)
2) one of it's injectors is bad. (Or the controller is bad)
3) There is damage to one piston.
If you are very good with a Di engine... it may be worth trying to fix it. BUT... the parts for the fuel injection system are very expensive.
What kind of ski is it? How much $$$ are they asking?