Machine stops after 2-3 stitches

Try to solate the problem to machine or foot control by detaching foot control and use stop/start. If stop after a start exhibits same as foot pedal then likely the problem is machine control board else, foot pedal. Could be foot control is sticking and not completely opening or slow to open.

Most likely it is a foot control problem--probably something you cannot see.

There's a possibility that your foot pedal is sticking; if that is the case, it's probably overriding the stop button. See if you can take the cover off and clean it using alcohol, and leaving it open for a couple of hours to make sure it has dried. Visually check the wires while it's open, too, to see if you can see any fraying, and make sure the plug on the machine side is firmly seated in the machine.

There are a number of things that could cause this.
Needle installed with flat in the wrong direction.
Excessive thread tension,top or bottom.
Lack of lubrication. If the machine can do anything more than a straight stitch the mechanism can gum up and not move the needle correctly.
Here is a link to threading directions.
Necchi 3537 Sewing Machine Threading Diagram

This is a good video on youtube about sewing silk.
http://www.youtube.com/watch?v=ijz_j7UXOik

If you can't adjust the bobbin tension, adjust the top tension. Also the lower thread needs to be pulled to your left (away from presser foot) before you start sewing, this avoids tangles.

A lot of machines have a speed control, either on the machine or the foot control. I looked thru the manual and did not find anything about speed control. Look under the foot control for a screw that may have a + and - . Otherwise, you may want to take it back to see if service can adjust it for you.

does anyb ody have a manual i can download

Usually pedals possess a variable rheostat controller that react with the action of your foot. If it fails to function normally, it suggests that a short circuit has occurred. Generally, that means an internal wire or contact opens up and stops all further activity as you mentioned. The best bet is to take the machine to your local sewing machine dealer for repairs.

your machine might have a problem with the rotary hook, it might need to get timed by a professional.