How hot is too hot?

[51 MERC-CT]

Originally Posted by Ritzy1

So, I've got less than 500 miles on my freshly rebuilt 59A-B flathead. .040 over, Merc 4" stroke crank, Isky Max-1, dual Stromberg 97s w/.091 jets, 185 thermostats, electric fan with 185 switch, 4# cap, dipped radiator. Before yesterday, it had been staying around that 185 mark, even in hot weather at highway speeds (65 MPH/1,580 RPM). Yesterday though, it was about 90 and I was cruising along at 70 or so and 1,680-1,700 RPM and it started to get hot . . . 206-207. I pulled off the highway, and it immediately dropped down. I got back on the highway, and cruised at about 65, and it went back to the 185 range. My question is, should I be concerned at 206-207? If not, what's the temp I should be concerned at?

Heating problems aside and out of curiosity, just what transmission, differential and tire combination are you using to achieve (65 MPH/1,580 RPM)?