Well Mr Opposed the ’51/’52 fasttwin were the “not so fast” fasttwin. I have one of those. I think it’s main claim to fame was its gear shift. The gearcase was shared with Johnson for the first time. The ’53/’54 fasttwin was a big improvement. Still not as fast as a Mercury but better than the 14s. The 15 had the throttle and the timing synchronized. These 15 were the start of some great running motors IMHO! I have two of those. This power head was used well into the 70s.
dale
“Crowded elevator smell different to midget!” Confucius