The Lehman "Operators Manual" covering the 80hp 4cyl 245cu/4150cc engine, designated 2712E, gives temp specs (same for the 6cyl normally aspirated and turbo engines) : range 175-195f/79-88C, optimum 195f/90C.
Note: 1. this is a different Lehman model reference to the one you quote and may be inapplicable.
2. I`m left wondering why the "optimum" is higher than the quoted temp range.
Anyway, I hope it is some help.
Island Gypsy 36 Europa "Doriana"