I only buy used engines from someone I know. Have not belonged to a club in years but remember guys starting big 4 strokes with the back flip method. Saw a video on the particulars a while back. Need to find it again.
Basically (having a decent running engine is assumed) it was just getting the carb nice & wet but not flooded with a few prop turns/choke. Turn prop in reverse to compression then back off a bit, throttle to mid range idle. Lite glow plug & give prop a quick flip and she's up & running.