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Guest Blog: Posted in comments RE: 4-stroke engines

Guest Blog: Posted in comments RE: 4-stroke engines

Author: Steve (IP:,




Ditto what Paul said.  I think the HKS-700E is darn near perfect for a “PSA” like the Merlin.  It’s a 4-stroke engine with 4-stroke reliability (I think most potential buyers of the Merlin would not want a 2-stroke), will get much better fuel economy than the 582, will require less maintenance (and no mixing of oil/gas), will still perform more than adequately on such a light airframe, will increase the range of the aircraft, and will allow the Merlin to obtain LSA certification if you eventually choose to go that route.

 Yes, the 0-100 Pegasus looks cool.  And it may ultimately be an outstanding engine in its own right.  But to-date it is unproven, not ASTM-certified like the HKS, and not backed by a large and well-capitalized company.  This presents a bit of a catch-22.  The 0-100 has to be sold and flown many hours before we can truly say it is a “proven” engine, yet I think many potential buyers won’t want to be the beta-testers who determine whether or not the engine is actually up-to-snuff.  It’s an age-old dilemma for small aircraft engine manufacturers.  If Pegasus can pull it off though, I definitely think there’s a market for an AFFORDABLE 60hp 4-stroke.

 And that’s really the only downside to the HKS.  It’s an excellent engine, and pretty much tailor-made for an aircraft like the Merlin.  But it’s not inexpensive when compared to the 582 or 0-100.  At least, in the short-term it isn’t.  But when you account for the HKS’s fuel savings over the 582, less required maintenance (plus no 350 hour overhauls), I’d bet that after 300-500 flying hours the HKS actually becomes the less expensive engine.  The trick will be getting consumers to think long-term rather than short-term.

 In any regard, nice work Chip!  The “PSA” concept has always fascinated me, even long before it was known as a “PSA”.  It’s sort of like combining the best of ultralights with the best of “real” airplanes.  I really hope this plane takes off (pun intended)!


Chip W. Erwin
South Lakeland Airport
Lakeland, FL

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Merlin-PSA-on-Amphibs merlin-on-floats DSCN4122 (00000002) Merlin-with-HKS-Engine



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