I use 32:1 mix in mine using good name brand outboard oil. If you want to baby the engine, 24:1 would be better, but you may see some of it in the wake you leave behind. I don't know of an external tank set-up. I just keep an extra gas can in the boat to top off the motor when needed.
im hving lots of trouble finding a impeller i checked the web. for the site posted on this forum i cant find enybody to talk to person to person
thanks charles w
Impeller for WF4 is same as Mercury part # 47-24447
There are several on line vendors who usually have
this available. AOMCI member Brian Wilcox manufactures hard to find impellers and other
molded rubber parts.
I have purchased impellers both from East Coast Marine Old Mercs and Brian.
Louis