We have a Yanmar 3GM that we have tried to hand crank on numerous occaisions. Despite releasing the compression tabs and having a hefty
winch gorilla swinging the handle, we have not been able to "fire it right up" at all. Nothing seems to work but the electric starter, so we have ramped up our solar charger so the batteries are fully charged all the time. We have no problems pushing the starter button, and if it has
fuel, the engine runs.