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They were made by Eska, & used Tecumseh power heads, try searching there. I used to have link, but can’t find it now.
I still have a 1970ish 5.5HP my dad bought new.
we ran it at 24:1
Maybe try calling these guys https://discount-marine-parts.com/ob_ted_williams.html
or it looks like these people will sell you a manual $4, that should have what you need
https://thebrazilianconnection.com/searsindex.html