1987 Evinrude 30HP coughs/backfires when cold but works like a clock once worms up

I got 1987 Evinrude 30HP electric start motor. I purchased it used two years ago. Motor is very clean. Seller said that motor was sitting in his basement for few years, and when I started it (Summer time) it was running a little rough, but nothing too bad, compression was good, so I bought it. I dropped it of for the guy (retired mechanic) who worked on my 15Hp motor before to " bring it up to a speed ". He had rebuild the carburetor, replaced plug wires, plugs and cleaned/flushed a lower unit (did not look like oil was replaced in last 10 years, maybe longer) and external fuel line needed to be replaced as it sucked in air. Motor started and ran like a champ on muffs when I picked it up in August and I left it alone until duck season.
NOW THE QUESTION - pretty much every time I would start my motor (Sept-December), it would take 4-5 attempts to start it cold. When it starts, it keep coughing/ backfiring, running high revs on Neutral and then drop revs, chokes and dies or almost dies, then pick up revs again .... very annoying... Once it worms up for 5-7 minutes it starts working like a clock and keep working fine all day long even if you let it cool off for 3-4 hours, starts, it start right away, runs smooth, etc.
PLEASE HELP.
Thank you

volf, what you are describing is more or less normal. The sneezing is caused by running too lean. It is too lean because it is not warmed up yet and cold engines require a tad more fuel. Setting the slow speed needle just a bit toward rich will help. It probably is set borderline right now.

But the real answer is don't be afraid to use the choke/primer to start it, and once it is started, momemtarliy "bump" the choke as required to keep it running more or less smooth till it warms up enough to keep running on it's own.

Hey, my own motor does it too, as well as many/most others out there.

Guys,
Thank you very much for your replies! I guess my confusion might be the part on how the choke really works on this motor. I also have 1980 15HP Johnson that has traditional simple choke system that never gave me cough thing.... pull choke lever out, start, push choke back 1/2 in once start worming up push choke all a way in, done..... Now, the 1987-30hp motor got choke/primer "all in one". If I pull choke out it feels like it has a spring that pulls it back in and as far I know it primes the motor. I read on-line that proper starting procedure of cold start on this motor is to pull the choke/primer lever 2-3 time to prime and start the motor.... so if you pull the choke an open hand to release it, it goes straight back inside.
FDRGATPR, I am not sure what you mean "momentarily bump the choke", it's probably the same thing that KIMCRWBR1 mentioned "Feather the choke", I am not just 100% sure on term and how it's achieved? Do I need to prime: pull the choke and let the spring pull it back few times to priming the motor, and then pull choke one more time and keep holding it back, fighting the spring keeping it from pulling back in?
I actual used Rich/lean knob and did try 1/4 turn towards Rich when started motor cold, but with the same luck.... Thank you

When you said electric start, I jumped to the conclusion that you meant it has remote controls with a key ignition switch. On those, you push in on the key to choke/prime it while at the same time turning the key to crank it. After starting, you would need to momentarily push (bump) the key again to give it an extra shot of fuel till it settles down.

Sorry for the confusion. I guess I have trouble thinking other people have different versions of the same motor.

yes, sorry it is a tiller motor with electric start. But I am sure that some sort of starting ritual needs to be in place for tiller same as remote controlled motor .... So maybe some one will comment on this one? Thanks