I've had the same motor since April, so I haven't encountered many really cold weather starts but what seems to work for me is just holding the key in for a few seconds while starting. Once the engine fires I release holding the key in and just let it idle to warm up. I do not advance the throttle or prime the bulb if I've used the boat within a week or so. If it has been over a week, I will use the primer bulb but only once or twice and no throttle - I do not squeeze the bulb until it is very firm. If I do, I usually flood the motor and it is difficult to start.

I did the typical internet research when I got the boat/motor and many do say it does like to be primed (firm bulb) but this did not work for me. Vary your approach until you establish a procedure that is working for you, but I recommend starting out with as little priming and choke as possible until you find the right balance. I did this in my drive way with the muffs on and quickly got it sorted out without being frustrated at the ramp. The motor runs great and I've been very happy with it.