gas in oil

I own a 2000 Yamaha 115 4-stroke. Lately, my oil level increases and it smells like gas in my oil. I have mistakenly been burning high-test with this engine. I only run it approximately 300 hours/year. I have never used ring free or any other additives. I'm looking for suggestions.
Thanks.

[boats.net]

Decarbon engine, change engine oil, check compression and have fuel system checked.