I forgot about this. I talked to the nice fella at Tacoma Marine, who specializes in Old Atlas-Imperials. He’s probably the best resource in the world on them.
After chatting with him, I’m convinced it’s an Atlas-Imperial. I found a cast part number on an intact cover that matched up to a common part number in three different parts manuals. But, couldn’t identify the specific model. Plus, being a west-coast Seattle made engine, in Hawaii made sense. Especially since quite a few old wooden, west-coast boats powered by Altas engines ended up in Hawaii.