Akin to the above situation, where spark plugs have continually become fouled, I have been experimenting with using 2 gas tanks for the last eight years now & for me I am happy with the idea. One, a 3 gal. tank, mixed at 100-1 with full synthetic oil & it is used ONLY FOR TROLLING, the other is the 12 gal. main 50-1 tank also used for my 70hp outboard jet on the same boat. Again, I am using the 100-1 synthetic only for trolling with the 9.9. If & when I need to run with this 9.9 motor faster, I simply switch to the larger 50-1 tank. However the winter of 2007/2008 in an emergency flooding situation, where I was rescuing a lady & her son who were stranded in her house & the water was still coming up fast, my main 70 hp jet water intake had become plugged with floating grass or hay, making it useless. It was getting dark & we were caught is a strong very swift current pushing me broadside to a fence, I did not have time to change the fuel tanks as I was broadside to the current & the 9.9 was then my only source of power then. I ran this motor at full throttle during the last half of this rescue mission for probably 20 minutes before I got to dry ground & offloaded the passengers. As of 2011, I am still using this motor with no apparent harm. But I was using the FULL SYNTHETIC oil mix.