I use a MDL-10 for each motor, or a MDL-20 if one fuse for both. They are slow-blow fuses, so they won't pop under the start-up load
The Doyle vacs had ABC-20 ceramic fuses on each motor, and within three months every one had blown for no apparent reason. They are electronics fuses - I don't know if they're a delay fuse, but obviously not up to the task.
In an emergency I've used a standard 20-amp automotive fuses, and they'll still blow before something burns up, but they usually melt under the metal cap just from the heat of normal draw from the motor running.