On page 24 of the owners manual the emissions warranty is stated as:
"The warranty period for this engine begins on the date of sale to the initial ultimate purchaser and continues for a period of five (5) years or 3,000 hours for 19-37 kW (25-50 hp) engines, and two (2) years or 1,500 hours for<19kw (below 25hp) engines, whichever comes first"
On the spec's page of the manual it states the engine HP as 24.5 but on 5 separate documents available on Massey's website regarding the GC2600/GC2610 the HP is stated as 25. With the level of conflicting published information with respect to warranty there might be an interesting case should someone wish to spend tens of thousands of dollars to save a few to obtaining a 5 year emissions warranty for the gc2600 should their tractor require it at some point.