@Al on our olde tub which is a family hand down and a very clean 1973 starcraft runabout with the dead reliable GM 6 banger I zap strapped a second spare belt down and around the front motor mount out of harms way.R
In December of 1980, I took my wife's brand-new Plymouth Champ from Boise to Sacramento for a fast-turnaround trip (Boise State won the 1-AA football championship). On the way home, in pitch blackness on Highway 95 north of Winnemucca, Nevada, the idler pulley froze up. This was a notoriously lonely stretch of 2-lane, and it was about 3 a.m., so there weren't even any truckers on the road.
I then figured out what I hadn't brought: any tools at all! So, no problem - just cut the belt off, right? Except: no knife. I figured that out there somewhere, there had to be a broken beer or pop bottle alongside the road. After walking nearly a mile in each direction, I found that I had stopped on the cleanest stretch of highway in America - not one bottle, can, gum wrapper - not even a sharp-edged rock. Remember, it was December, in the high desert, and I was starting to get desperate. I also had to be to work the next morning!
So, unable to cut the belt off, I decided to just run without lights or heater or radio - to preserve battery power - and let whatever happened, happen. The belt smoked and squealed, but things held together all the way into Jordan Valley, Oregon (everything else was still buttoned up and dark along the way, except for the lights over a few cattle watering troughs on ranches). It was nearing dawn, and I borrowed a socket wrench at a gas station to remove the belt and paid them $2.50 for a quick battery charge while I ate at the cafe. After a quick scoot home, I was only about 40 minutes late getting to work, and the Champ was outfitted with a small tool kit and extra belt the very next weekend!