Mercury 150hp 2 stroke EFI help

Although my Mercury 150hp 2 stroke EFI runs like a dream, uses little oil and fuel and don't smoke much (for a 2 stroke), there is one niggling issue that I have with it.

 

After shutting down warm, I always need to push in the neutral button, put in some throttle, before I can restart it.  If I don't do this, it will crank but not fire up.  New spark plugs did not help.

I think I read somewhwhere it has something to do with vapor lock?  Is there anything simple I can fix this?  If not, no big deal as everything else is running smooth.

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 Haines Signature 610C with Mercury 150 EFI