Hand cranking
Nearly all engines of this type -- including some you may never had heard of like Bukh for instance -- have provisions for hand-cranking, but you oughta give it a try sometimes so that you may fully savor what true folly this really is!! It's definitely not your Grandad's Model T and it's something that is provided strictly for an emergency. You will also find that you can risk some fairly substantial injury by hand-cranking the engine once the engine starts -- if it starts -- and the crank in still engaged along with your hands!! Best bet, as long as your starter is operational, is to carry a back-up battery like those you see in the auto stores or run separate house and starter batteries with the ability to isolate them. You can also get devices that attach to your cranking batteries that disconnect the batteries if the devices determine there's a DC leak which is draining your battery voltage. Flip a switch and you're back in business for starting the engine. If you are cruising or interested in carrying a spare, well, scrounge around and find your a spare starter, have it rebuilt and shrink wrap it protect it and keep it aboard in case your primary goes kaput. Carry the hand crank, too, for extra insurance, but plan on counting on it only if you are down to the very last resort. Good luck.
