I don't know how much longer it's gonna take for folks to get over the whole 87 octane/E10-15 - outboard scare propaganda.....but whenever you do I just want to be on record (for the last 2+years) of telling you that it's BS.
Yes yes I've seen the split open primer bulbs sitting on marina counters all over the country,.... but here's the deal ; Go buy some 87% fuel that you wouldn't dare burn in your outboard because of what you've read, been told, or been shown by others in the industry, then go buy the cheapest primer bulb on the market (like a Tempo from Wal-mart) or even one that's been in your garage trash can for three months and go soak that rascal in that "poison fuel" and see if you can make it look like that one you saw displayed wherever you get your boat worked on, using nothing but that fuel.
After you fail to see that rubber turn to mushy goo try again, but this time add some Stabil, Seafoam, Carbon guard, 24C, or one of those other "recommended" additives that you hear everyone praise so highly, and see if you have better success melting rubber.