A pilot ferrying an AT-802A reported an engine fire and diversion to a nearby airport.

Narrative

Incident report engine fireAircraft AT802A ferry flight/delivery flight ZZZZ- ZZZZ1.Flight leg ZZZ - ZZZ1; initially VFR; than re-cleared IFR; for the oceanic clearance to ZZZ1; I did test HF radio comm but was not able to establish proper radio contact; therefore; ZZZ ARTCC XXX.XX did cancel my clearance; so I have had to head back to mainland; my diversion airport of choice was ZZZ2; where I was hoping to get the radio fixed. The engine fire event developed.About 20 minutes after leveling off; I had tried to establish HF radio contact; but it turned out no communication was possible; therefore; after several attempts; ATC cancelled my oceanic clearance and 'forced' me back to mainland.Anyhow; as I was checking and cross-referencing the aircraft performance; I noticed I might not have been able to make it safely to the planned destination; rather; I could have reached the destination; but only with the bare minimum amount of fuel; in my opinion and experience; the decision of cancelling the flight was the most adapt according to the developing situation.And so; about 2 hours into the flight; and already over the mainland; blueish-whitish smoke started exiting from the right muffler (pilot P.O.V.); in great amount; almost immediately; flames became visible; apparently exiting from the right muffler and seemingly burning around the welding area of the right muffler.No loss of power nor performance were noted; the engine continued delivering performance; oil temperature and pressure were always in the green band; as Ng and ITT (Interstage Turbine Temperature). Anyway; as a precaution I decided to reduce power and slow the aircraft down to the minimum cruise speed; whilst monitoring and assessing the situation. I did advise ATC; ZZZ approach XXX.XY (if I remember correctly). Thanks to the good coordination of the controller in duty; IFR flight plan was cancelled and VFR clearance was [established]. I had to descend from the then-current cruise altitude to a lower one; as with reduced power setting I was not able to maintain. As soon as I cleared the topography; I decided to look for the first available airfield and land; being ZZZ3 airport.After landing; once at parking and after fuel cut off; I went to assess the situation; as apparently; flames and smokes were still present; same location; same intensity. I then did discharge the halon bottle part of the cockpit equipment. The visible flames were almost extinguished. Over the next three hours after parking; I took care of tearing down all the ferry equipment; always monitoring the status of the fire; and I can confirm all flames and smoke disappeared about 10 minutes after the halon discharge.