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  1. #1

    Default 2010 Merc 30hp EFI 4S occasional stall when returning to neutral or low rpms

    I'm really starting to pull my hair out trying to figure out why my 2010 30hp EFI keeps stalling when returning to idle. Not always, more often than not it is ok, but it stalls enough that running in a river with strong tidal currents, I'm losing faith in the motor and letting my kids use the RIB it's on.


    Last season, right after I bought the boat/motor used, I definitely had fuel issues, as the fuel system was dirty. I added a Racor fuel/water filter, changed the low and high pressure fuel filters, cleaned the VST tank and screen, and had the injectors tested and cleaned and screens replaced. I also tested fuel pressure on the rail and it was perfect. New plugs too of course, and new impeller. Went through the whole thing. It performed MUCH better, but the season was over, so I thought I solved all the issues.


    So far this season, it still has the occasional stall when returning to idle quickly, or going to neutral. I changed out all the garbage gray fuel lines to low permeation rubber fuel lines, and have fresh fuel. The only thing I can think of is maybe the Idle Air Control valve is sticking, so sometimes it's ok and sometimes not? I looked at that last season and it appeared to working just fine, as I could hear it pumping and operating so I didnít change it. Or is there a interrupter switch that could be failing? Someone recommended my throttle body may need to be adjusted but the service manual says itís not adjustable.


    When you bring it back to idle, it may drop to 600-700 and then catch and not stall, or sometimes it will hunt a bit and catch or sometimes it will just die. Hard to catch a video, because most times it's fine. Seems like the faster you return to idle speed, the more likely it is to occur.


    Any thoughts or guidance would really be appreciated. I thought going to an EFI would solve a lot of the pain the neck issues I had with my old 2 stroke, but so far this hasn't been the case. Thanks a bunch.

  2. #2
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    4,362

    Default Re: 2010 Merc 30hp EFI 4S occasional stall when returning to neutral or low rpms

    IAC could be sticky or dirty. Remove and spray it down with TBC (throttle body cleaner) paying attention to plugger and pintle tip. Shake it dry and reinstall and run it several times.
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  3. #3

    Default Re: 2010 Merc 30hp EFI 4S occasional stall when returning to neutral or low rpms

    Thank you. Plugger and pintle tip? Not sure what that is. Not the easiest to get at on this motor, but should be able to.

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