Sounds like it's running out of fuel, runs long enough to use what is in the bowl and not getting more from the pump or fuel line. Is it on a separate tank and is the vent closed? If on a self contained tank is there a good supply of fuel coming from/thru the line from tank to carb? Is the new carb well sealed at the mounting flange, could it be sucking air thru a vacuum leak? Does it start right back up if fuel is induced into the carb? That would rule out electrical problem. Engine needs 3 things to run, fuel, fire, and compression. Sounds like it is running out of one of these. Since it starts is has compression, and fire is not likely to quit that soon (15 secs), so fuel is logical answer. Try hooking carb to alternate fuel source, if same problem may be the float valve has some debris in it. David Doyle www.CruisingTheGreatLoop.com In a message dated 3/28/2012 8:31:40 A.M. Eastern Daylight Time, circumnavigate06@bellsouth.net writes: I have a looper at anchor behind my home. He was awaiting weather to cross to the Bahamas when his 10 year old 4 stroke, 4 hp Mercury outboard failed to start. He asked if he could set it up in my yard until he figured out the problem. Since then he has installed a NEW carburetor. It now starts, but stops after about 15 seconds. I have no ideas for him - perhaps somebody in this group can help him out, or I will have to take him to a mechanic, which both of us are reluctant to do. Any ideas fellows? Tommy _______________________________________________ http://lists.trawlering.com/mailman/listinfo/great-loop_lists.trawlering.com To modify your Great-Loop subscription options (change email address, unsubscribe, etc.) go to: http://lists.trawlering.com/mailman/options/great-loop_lists.trawlering.com