Re: 175 hp merc 1987 primer bulb
Actually, it's a little known feature in most machines called a critical needs indicator. At the end of a day, you're under pressure, (need the biffy) you're tired, your wife is antsy about the meat in the slow cooker, and you just need it to idle onto the trailer in a well behaved way one more time. The critical needs detector senses this and shuts it down.
It's the same device that makes the dollar bill changer in the coke machine spit your bill back when you are really, really thirsty.
Seriously, it's usually just tune in general, maybe coupled with an attempted start with the engine tilted up near the end of a tiring day, and it'll load up. If I mess up like that, when I get it started I take a 10 second WOT loop before I stuff it on the trailer. Just seems to make the durned thing happy and well behaved.
hope it helps
John