The 9 cubic inch 92908 was advertised as 3.5 hp until 1982 I think. Then both 92908 (PulsaJet version) and 92508 (VacuJet version) were derated to 3 hp. The explanation Briggs gave focused on the fact that they had to reduce the maximum governed speed of the vertical crankshaft engines from 3,500 rpm to 3,000 rpm because of safety concerns relating to blade tip speed and how hard the blades could throw stones. The horizontal crankshaft versions continued to be governed to 3,500 rpm. I don't recall them increasing the advertised power of the 9 cubic inch vertical crankshaft engines after that, but I could be wrong. Nowadays they avoid referring to power output, having lost a lawsuit on the subject of advertised power. They got away with it for several decades before that happened. The advertised 3 hp was probably less than 2 hp when the engine was trimmed and fitted to a mower. Briggs was not the only culprit - it was usual practice for engine manufacturers to advertise gross power, not nett power. The same thing was done by car manufacturers up until the 1970s, then they switched to nett power to avoid the same kind of litigation that the small engine people encountered in the 2000s. So, if you know someone with a 1960s or 70s muscle car who brags about its power, just snigger a bit and move on. The horses were very small ponies in those days.
