Re: 5 hp Viking/seized and then…

[Don]

How do you know it is not the gearcase that is seizing? Just because the prop shaft spins does not guarantee the driveshaft isn’t seizing up. Have you drained/changed the gear lube? I’m not sure just what vintage of OMC components your engine has, so can’t make too many specific recommendations. If the powerhead is seizing, this is usually due to not enough oil or overheating.
Don’t think there is much to lose by trying the engine again. Be sure to drain/refill/inspect the gear lube and mix at 16:1