Viton is the best affordable material that is ethanol resistant. They list a Viton seal. The preferred color is brown which they show. OMC used Viton seals & gaskets in brown color to signify Viton. It is normally expensive vs regular (buna N) material.
There are a lot of thing that go into a quality seal, but for this cheap price might be worth a try. I would not put them in the gearcase as there is no mention of the case being stainless steel. Chris P. has tried that & found they don’t last. JMHO

Dan in TN