Hi
Could someone please tell me if there is a difference between a black Merco .40 and the regular Merco .40?
Thanks
Dwayne

Yup, I can comment on this one. The first side exhaust Merco 40 was with the original width bypass, and so far as I know, was natural finish. Later the bypass was enlarged greatly, (also the 29, 29diesel, and 35), and I know these as black anodised. There may be some transition engines, possibly original bypass/black, but more likely large bypass/natural. The only difference technically is the bypass width. Theoretically the large bypass may give more power, but bearing in mind all the bits of wood, chewing gum, araldite, epoxy, etc. which folks use to reduce bypass area in some engines, this may not be an improvement for stunt.

Andrew's comments are worth noting. Bear in mind that Merco has had various owners and various build qualities over the years. Dwayne - best to asses your motor on its own merits. It may be great, it may be not so great. During the bad periods, the point is the engines were aimed at the r/c market, where the owner would stick a starter on it and basically it could not fail to run and give some sort of adequate service.