Re: What Size Fuel Line?
Certainly you mean 3/8 not 3/4. Anyway, if 5/16 is enough, you won't see any difference by going to 3/8. On the other hand, if 3/8 is required, you WILL see a difference, possibly even engine damage, if you use too small (5/16).
Is 3/8 required on your 70hp? Probably not.
Bottom line: 3/8 can't hurt. 5/16 can.