For those interested, some excellent information has been received re Undocumented Outboards No's 1 & 3 from Collector Inspector and Croweater of SOS . Many thanks to both gentlemen for their support.
Undocumented Outboard No 1. is now confirmed to be a owner build using readily available parts. The 'Simplex' gearbox and join in the exhaust tube, as well as the name and model number which actually belong to a model aircraft engine gave the clues needed to establish the above claim.
Undocumented Outboard No 3. is a Regcraft I/O unit. The articles and adverts below answer most questions about this super rare unit. Hope you enjoy the read.