I have a fairley new mercury 25hp tiller motor it has a carburator with a primer built to the side of it and a nob that you pull to prime it the motor is very hard to start and i have great spark i was wondering if anyone new how the primer works and what steps to use to start the motor?
prime your line with the bulb til it's hard. Pull that knob a few times and you should hear a "squirt" sound in the carb. Push the knob back in all the way (no choke), half way (half choke), or all the way out (full choke) to start the engine. You should feel a series of clicks in the knob when pulling it out. With it all the way seated, it's not choked at all. The next click half and the third is full, then after that is when it hits the primer. Just remember when you use the primer, you have to push the knob back in....or your pretty much running the motor choked. Also, if it's hard to start, buy a carb kit and clean the carb inside and out...change the plugs, and that will put it back in order. It's a great motor, keep it up and you will have it for many many years.
On the face / top of the carb is the screw. It only has one, it's the only carb adjustment for the air fuel ratio. Merc manual says to seat the needle lightly, then back it off 1 1/4 turns, then 1/4 turn in either direction to get the best mixture. Turning it in makes it richer and out makes it leaner. You want to be on rich side. Not on muffs, but in the water....start with the screw at 1 1/4 turn from seated, crank the motor, and adjust the screw to the lean side (out) until it begins to die, then back to the rich side (in) until it begins to die...back it off slowly until it smooths out....then you've got it. Thats how to set it at idle.