I just bought a jon boat with a 1978 25hp evinrude on it, it runs great and had a full tank of gas in it. I asked the guy i bought it from what ratio he mixed it with he said he thinks 40:1 but not for sure. I want to make sure i get it right, does anyone know what it is supposed to be?

My old '56 Evinrude 9.9hp was 1 pint to 4 gallons. My '67 Evinrude 80hp is 1 pint to 6 gallons. Better check with a mechanic in on this.

Or , I'm sure someone will come up with the answer here soon!!

I have a 1979 Evinrude 25 HP  50:1

40:1 wont hurt it, it just will smoke a lot more.

It's not the year model motor that really determines the mix ratio, it was the oil they had available when that year was made.    Two stroke outboard oils have come a long, long way from the 50's and 60's.   With todays TWC-3 oils, most any motor turning less than 6,000 rpm can run a 50:1 ratio, even the old 50 models that required a 25:1 ratio when they were built.   Back then, about all they had was basically 30W motor oil so it took a lot more of it to get even close to the same protective oil film TWC-3 will give today.

Just be sure you use TWC-3 in water cooled engines (that's what the WC stands for, water cooled) and use regular two stroke oil made for air cooled chain saws, weed eaters etc in the old, small air cooled outboards.  Also, don't use your TWC-3 in air cooled chain saws, weed eaters etc.

Thanks for all the input.

I'm pretty sure my Dad's engine is a 78 35hp Rude and his has always been 50:1.