2000 Sea Ray 21' 5.7 Mercruiser MEFI 1 TBI Runs rich always

Discussion in 'Sport Boats' started by Al Schmitt, Jan 19, 2020.

  1. Al Schmitt

    Al Schmitt New Member

    12
    Jan 19, 2020
    2000 SeaRay, 21' 5.7 Mefi 1. Runs rich always.
    5.7 Mercruiser TBI
    I have a boat in the shop I just can't figure out. It's a 2000 Sea Ray, 21' with a 5.7 Mercruiser MEFI 1 TBI.It runs rich always. Customer states it ran well when put into storage last year, has run rich always since being put into service this last session. Engine appears to be in good health with 180 psi of compression and less than 5% leak down. I have installed a new fuel pump and regulator which brought fuel pressure into spec at 30psi. All the ignition has been replaced except for the coil which has good output. The injectors have been cleaned with no difference in operation. I tried automotive injectors which made it run worse. I do have an automotive MAP sensor installed with no difference. All sensor readings are in spec with the Mercury scan tool. Injector milliseconds are at 2.2 when idling rich. Vacuum is at about 12"hg when idling poor and goes to 17 under load. I seen a great post from 2010 but they didn't finish with the result. Does anybody have any ideas? Any information would be greatly appreciated!
     
  2. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    What is the recommended thermostat for this motor?

    Is it installed and operating properly?

    Any issues with the coolant temperature sensor? I think there are 2 of them in the thermostat housing.

    The 2 wire sensor is for the ECM and the one with one wire is actually just a sender for the dash gauge.
     
  3. Al Schmitt

    Al Schmitt New Member

    12
    Jan 19, 2020
    2000 SeaRay, 21' 5.7 Mefi 1. Runs rich always.
    5.7 Mercruiser TBI
    The dash gauge and the sender for the ECM are reading correctly. I wiggle tested them,also tried sensors from another boat with no change. I thought that also, thinking maybe the ECM thought it was 30 degrees. It does run best on initial cold start, then runs worse as it warms up.
     
  4. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    How were the injectors cleaned?
    A bottle of injector cleaner in the tank, or were they removed, flow tested and rebuilt?
     
  5. Al Schmitt

    Al Schmitt New Member

    12
    Jan 19, 2020
    2000 SeaRay, 21' 5.7 Mefi 1. Runs rich always.
    5.7 Mercruiser TBI
    I removed them and backflowed them with a 9 volt battery and carburator cleaner. It did seem to make a slight difference for the better. When using a timing light pointed at the injectors, they do seem to have a heavy spray pattern although both are the same pattern. I'm hesitant to replace them with Mercury injectors due to the cost of $1145.00 each. I could swap a complete throttle body from another boat and retest.
     
  6. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Figure out why you only have 12" of vacuum
     
    techmitch likes this.
  7. Al Schmitt

    Al Schmitt New Member

    12
    Jan 19, 2020
    2000 SeaRay, 21' 5.7 Mefi 1. Runs rich always.
    5.7 Mercruiser TBI
    That does concern me. The needle in the gauge does bounce a little between 10 & 12"at a very poor rich idle. Maybe that's where the problem is. Maybe it can't get enough good air in. I have checked for exhaust restrictions and found none.
     
  8. Al Schmitt

    Al Schmitt New Member

    12
    Jan 19, 2020
    2000 SeaRay, 21' 5.7 Mefi 1. Runs rich always.
    5.7 Mercruiser TBI
    When I advance the timing to about 55°, it runs better under no load. Could it be the timing has jumped? The motor has about 1000 hours on it.
     
  9. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    It's idling rich cause you have a vacuum problem.
    Bouncing needle means bad valves
    Low vacuum probably an air leak
     
  10. Al Schmitt

    Al Schmitt New Member

    12
    Jan 19, 2020
    2000 SeaRay, 21' 5.7 Mefi 1. Runs rich always.
    5.7 Mercruiser TBI
    Thanks so much for the help! I'll look at that closer.
     
  11. Arminius

    Arminius Member

    60
    Oct 30, 2019
    Seattle
    Bowrider 200 Select, 2003
    5.0L MPI, 260 hp w/Alpha 1 Drive
    On a similar rig, with a similar problem, I had a bent throttle plate! I always assumed it was from a horrendous backfire.
     
  12. Al Schmitt

    Al Schmitt New Member

    12
    Jan 19, 2020
    2000 SeaRay, 21' 5.7 Mefi 1. Runs rich always.
    5.7 Mercruiser TBI
    Thanks, we're bringing it in now to take a closer look.
     
  13. techmitch

    techmitch Well-Known Member GOLD Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    Yep, base engine problem.
     
  14. Al Schmitt

    Al Schmitt New Member

    12
    Jan 19, 2020
    2000 SeaRay, 21' 5.7 Mefi 1. Runs rich always.
    5.7 Mercruiser TBI
    I would like to thank all that helped out with this rich condition. You guys were right on with a base engine issue. Turned out to have a blown head gasket on the starboard side, between the #4 & #6 cylinders. Thanks again for the help.
     
  15. Arminius

    Arminius Member

    60
    Oct 30, 2019
    Seattle
    Bowrider 200 Select, 2003
    5.0L MPI, 260 hp w/Alpha 1 Drive
    Have you had it in the water yet?
     

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