It depends on the nature of the vehicle. Certainly, a Briggs-n-Stratton lawn mower engine can choke down some pretty polluted fuel. Modern car and truck engines have an array of sensors that adjust the timing and a bunch of other stuff to accommodate the fuel. Boat engines, even Honda, aren't as sophisticated, even if they have as their basis the same block. I would imagine the Honda 130 runs a fairly high compression ratio and its runtime parameters are pretty close to design limits, so you are in the danger zone.

Given the cost of outboard repairs, I think it would be wise to replace the fuel. Even if the motor is under warranty, I bet they could back out if they find out the fuel was 5 months old.