Best Octane for older 2 cycle motors

What is the best Octane rating should I use to mix 50:1 ratio with?
I am thinking of the higher 92 Octane! However I have a smooth running 1969 Merc40 and don't desire to burn it up with too hot of fuel.

Thanks for your time.

87 is fine. Others seem to have alcohol in the fuel, VERY bad for fuel lines.

I have a 2000 25hp Merc that I run 87 octane & a 1974 85hp Merc that I run 93 octane in.

I believe that 40hp would be good with the 87 octane providing the timing is set at factory settings.

No need to purchase premium however the 89 octane has enough knock resistance to be comfortable with for the long run. Knock in a two-stoke is almost instant death to one so I use 89 octane........period.
Even back when I drag raced boats, with the high compression ratios we were running the 89 octane produced the best power.

Here in NC most all gas stations have Ethanol in all of their gas. I have to drive 20-30 minutes for Ethanol free gas. I do run 87 though in a 99 Johnson 15. Here is a great website to find Ethanol free gas near you. https://www.pure-gas.org

Leaded race fuel is probably the best. But $7.50 a gal isn't cheap. It doesn't go bad though. Or 100LL from the airport. Seems to last a good while and no ethanol...that I know of. I figure if we get 4 more years of moron socialists in office, we'll probably see a ban on leaded race fuel and 100LL.

Currently working on converting a Yamaha F25ESH to Methanol. Just for fun. I still have the (perfect) stock carb for it so I can go back. Up & running...picked up 3.6-3.7 mph and much more responsive but still a hair fat on the midrange. Good up top and great idle but fat in the middle. Working on that.

minimum octane i can buy anywhere in my country is 92 and it is all ethanol mix. i clean the e10 in a home made phase separator. result is alcohol free fuel with lowered octane. no idea about the exact octane rating of my "purified" fuel, but no problems so far....... i can only brew small batches at a time so it's ok for the small motors i use, it won't work though when i move on to bigger motors.