This 06 50HP Mercury is driving me insane with a cold start, all had been working well but recently when I go to start up the first time of the day, I’m having to choke it at about 1/2 throttle fires right up and the rest of the day we are good to go. Starting it without moving the throttle down, it’ll start to turn over and then just die on me. Recently changed fuel lines too but doubt that’s an issue.

Did you change the primer bulb? Put it in the correct direction? Use a good quality bulb or cheap aftermarket?

My 50 Merc was like that the whole time I owned it. It always wanted some choke and or some throttle to start cold.

It’s all nicer lines and bulbs, the old one was the Eva material cheap

My 2009 50 Merc is like this every start also.
I do put in a can of Seafoam for every five gallons of 87 octance gasoline.

Have you tried using ethanol free gas?

Im running seafoam as well as ethenol treatment with super premium maybe overkill but oh well

I've always had to choke the 150 VMax to start. Once it turns over she's good to go for the rest of the day. The longer she sits the longer she needs to be choked. (gee that could read really wrong)