Merco 61 Mk IV, an excellent 1970's English glow engine - review & test run

A look at and test run of a Merco 61 Mk IV, an excellent 1970's English Glow engine, of the old crossflow designs, with a steel cylinder liner, and a ringed aluminium baffled piston. It has a twin needle carb and twin bearing. The engine is fitted with the Merco Peak Power muffler, which was released in 1968 along with the Merco 61 Mk III. The Mk IV engines were produced from 1973, but there origins, the Mk I was produced in 1964. Sadly Merco, like so many other glow engines, are no longer produced. The engine is fitted with a 11 x 6 Master Airscrew Prop, the fuel is 7% Nitro, with 20% oil. The oil is a 50/50 synthetic and caster mix.