Here is a link to possible years. It show 1936, 37, and 38 as opposed twins Seakings at 4.8hp and Thor as the supplier. (Im not sure if my assumption is correct)
My guess is that it’s a 1939 5 horse made by Evinrude. The Sea Kings were sold as Vikings up here in Canada. The 39 was a model 466 (I think the Sea King was a 499?)
Have a look at Richard Paquette’s site – there’s a good picture of the 466 in Viking colours: