Re: 1951 5hp montgomary ward sea king model 15gg9015
Howdy, kom1c,
Welcome to iboats.
That engine was made for MW by Gale, a division of OMC (Johnson/Evinrude) and is quite similar to JohnnyRudes and Gales of the period. At different times and from different sources fuel spec has been 16:1, 20:1 or 24:1.
The most recent spec I have seen is from BRP, current owner of brands that were made by OMC in the past. That is 16:1.
I don't know why it was changed from 24:1, where it was for about 50 years. If I had it I would be using 24:1, but that would be taking a risk by not following BRP instructions.
Safest bet is 16:1, 87 octane gas and TC-W3 outboard oil.