I have a 2010 merc 250 XS. it runs great,but when i stop and fish for a while and then try to start it again,its hard to start.Then when it finally does start,it idles way up and smokes and the alarm goes off.After about 15 seconds it returns to normal.Can someone please tell me what is going on,Im very frustrated.

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read or post there and you'll likely get better/more info

Move this topic to the boats/motors section of this forum. Usually some mechanics floating around down there that might can give you a starting place to look.

my old 250xs did that a few times.

had a pebble stuck in the thermostat. made the engine richen itself.

pull the port side t-stat and see if anything is in there.

I also have a 2010 200xs that was doing the same thing...took it to shop and it was a pebble stuck in the thermostat....also they told me i would have to blow it out with air... not water....hope that helps...

Sounds like a leaking injector or water temp sensor. I do`nt see it dumping enough fuel into the motor to not start from a pebble in the thermostat but have seen stranger things.

Could be the fuel tracker valve diahragm in the fuel rail. It is probably cracked and leaking fuel in the cylinders when it is not running.

Thanks for the input Guys.I brought it to Master Marine in San Antonio yesterday.Hopefully they can figure it out.