just some extra random thoughts also

since the link above is an ancient, 60 year old boat, it occurs to me that finding such a vessel with an old school diesel engine with minimal knots on the clock is highly probable, and the old school diesel engines don't depend on electricity to function, everything is mechanical and thermal... and a smart guy knows that at a pinch you can just throw any vegetable oil or even tallow in the tank (presumably need to be blended) and go, and making actual biodiesel in post apoc situation isn't even that hard to do if you can construct a good pearl ash furnace to burn wood down to white mostly potassium hydroxide... which you can then mix with water and hydrolyse these fats and then using a separatory device, simple as a syphon carefully deployed... i mean

engine will still work after the global killshot, just need to stack diesel in the tank and in emergency can dock anywhere near human settlements and probably find either diesel or tons of shitty rapeseed oil and fill up and off you go