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  1. #31
    Join Date
    Aug 2009
    Location
    Mt Airy, MD
    Boat
    Searay
    Details
    340 Sundancer
    Engine(s)
    Twin 8.1 Horizons
    Posts
    371

    Re: Mercruiser 7.4 MPI Engine alarm

    Connie, you bet. Please let me know what they tell you. I've found a lot of "symptoms" posts with no resolution! :)
    "LindSea II"
    '04 340 Sundancer, 8.1 Horizons (Current)
    Gunpowder Cove, MD
    Previous
    '03 280 Sundancer, T5.0 B3s (Previous)

  2. #32
    Join Date
    Sep 2008
    Location
    SWEDEN
    Boat
    Sea ray
    Details
    2002 340da Checkmate 242 convinsor Dodge ram quad hemi 4x4
    Engine(s)
    6,2 mpi vdrives
    Posts
    16

    Re: Mercruiser 7.4 MPI Engine alarm

    Im having the same problem with my 5,7efi -97
    alarm goes at 2500rpm and the engine reduces power.

    was it the knock sensor wire that were your problem?

    I didnt tought the alarm can sound because of the knock sensor.

  3. #33
    Join Date
    Aug 2009
    Location
    Mt Airy, MD
    Boat
    Searay
    Details
    340 Sundancer
    Engine(s)
    Twin 8.1 Horizons
    Posts
    371

    Re: Mercruiser 7.4 MPI Engine alarm

    I don't have a reduction in power. Based on this information that I found at another site I think it can alarm. I'm not positive though. I have yet to isolate it down to which sensor. I do know it's on my starboard engine.

    I can't take credit for this information - I'm only passig it along.

    ======================

    Here it some general information I put together about the warning horn systems on Mercruisers for someone else.

    PS, Your particular engine does not have everyone of these Warning system Faults, But it has a lot of them, The best thing to do is to have a service manual from mercruiser for your engine to help you know what your engine really has as far as sensors go.


    The 2 beeps per minute can be generated by quite a few things. Some of the error conditions will limit the available power the engine produces. The 2 beeps/minute can be generated by: cam sensor open or shorted, engine cooling temperature circuit open or shorted, coil harness wire (EST) open or shorted, fuel injector open or shorted, IAC output, knock sensor, MAP sensor, MAT sensor, oil pressure circuit open or shorted, port/starboard exhaust manifold cooling temperature circuit open or shorted, sea pump circuit open or shorted, fuel pump relay, throttle position sensor circuit open or shorted, low 5 volt power supply as well as other errors.
    Best suggestion for the 2 beeps per minute is to have the dealer/shop read out the error log to see what is generating the error condition.

    This table is a guick guide, showing what warning output will accompany a fault for the Mercruiser Sterndrive engines. (MCM)

    Warning system Faults, SC1000 Yes/No, Audio Alarm, Available Power %, Description.

    (1) Cam Sensor Yes 2 Bp/min 90% Open or short, engine must be cranking to set this fault code.
    (2) ECT CKT HI Yes 2 Bp/min 90% Open
    (3) ECT CKT LO Yes 2 Bp/min 90% Short
    (4) ECT Coolant Overheat Yes Constant 6-100 % Engine guardian overheat condition
    (5) EST 1-8 Open Yes 2 Bp/min NA Coil harness wire open
    (6) EST 1-8 Short Yes 2 Bp/min NA Coil harness wire short
    (7) Fuel Injector 1-8 Open Yes 2 Bp/min NA Fuel injector wire open.
    (8) Fuel Injector 1-8 Short Yes 2 Bp/min NA Fuel injector wire short
    (9) IAC Output Yes 2 Bp/min 90% Only with rpm
    (10) Knock Sensor 1 Yes 2 Bp/min 90% Alarm sounds for 20 seconds in NEUTRAL and indefinitely in gear.
    (11) Knock Sensor 2 Yes 2 Bp/min 90% Alarm sounds for 20 seconds in NEUTRAL and indefinitely in gear.
    (12) Low Drive Lube Strategy Yes Steady Bp 0-100% Low oil in sterndrive.
    (13) Low Oil Pressure Strategy Yes Constant 0-100% Low oil pressure strategy.
    (14) MAP Sensor 1 Input High No 2 Bp/min 90% Short, no visual on SC1000.
    (15) MAP Sensor 1 Input Low No 2 Bp/min 90% Open, no visual on SC1000.
    (16) MAT Sensor Yes 2 Bp/min 90% Open or short in MAT circuit.
    (17) Oil PSI CKT Hi Yes 2 Bp/min 90% Short, defaults to 51.7 psi.
    (18) Oil PSI CKT Lo Yes 2 Bp/min 90% Open, zero oil pressure.
    (19) Overspeed Yes Constant RPM Limit Engine over rpm limit
    (20) Port EMCT CKT Hi Yes 2 Bp/min 90% Open, defaults to 32 degrees F.
    (21) Port EMCT CKT Lo Yes 2 Bp/min 90% Short, defaults to 32 degrees F.
    (22) Port EMCT CKT Overheat Yes Constant 6-100% Overheat condition, 212
    degreesF(100 degrees C) limit.
    (23) Sea Pump PSI Lo Yes Constant 6-100% Low water pressure strategy, defaults to 43.4 psi.
    (24) Sea Pump CKT Hi Yes 2 Bp/min 90% Open.
    (25)Sea Pump CKT Lo Yes 2 Bp/min 90% Short.
    (26) STB EMCT CKT Hi Yes 2 Bp/min 90% Open, defaults to 32 degrees F.
    (27) STB EMCT CKT Lo Yes 2 Bp/min 90% Short, defaults to 32 degrees F.
    (28) STB EMCT CKT Overheat Yes Constant 6-100% Overheat condition, 212 degrees (100 degrees C) limit.
    (29) Steer CKT Hi Yes No No Open and short.
    (30) TPS1 CKT Hi Yes 2 Bp/min 90% Short, signal to 5v+, engine will not start. Refer to data monitor screen.
    (31) TPS1 CKT Lo Yes 2 Bp/min 90% Open.
    (32) TPS 1 Range Hi Yes 2 Bp/min 90% Above 4.8v, 994 counts.
    (33) TPS 1 Range Lo Yes 2 Bp/min 90% Below 0.5v, 35 counts.
    (34) Trim CKT Hi Yes No No Short, high range, visual warning on SC1000 only.
    (35) Trim CKT Lo Yes No No Open, low range, visual warning on SC1000 only.
    (36) 5 VDC PWR Low Yes 2 Bp/min varies Short any 5v+ to ground.


    Here's some other information that what will sound the alarm on a mercruiser Engine.
    Constant tone alarms are for:
    1.) engine coolant temp overheat,
    2.) low engine oil pressure,
    3.) engine overspeed,
    4.) exhaust manifold cooling temp overheat
    5.) sea pump PSI low.
    Note #5 is known to be a common problem, It's been said that this fault might not show up in the fault history section of the scan tool.
    If that is the case then the only other way to know if this is your problem, is to watch this sensor live as it happens out on the water with the scan tool hooked up to the engine.
    Also make sure all the Battery cables are clean & tight plus a fully charged Battery is very important.
    Check the water pressure sensor threads for any paint, Also check the sensor to see if it has come loose or Has a blockage of some kind.
    If any sensor loses it's ground it could sound the alarm. As an additional test, try adding a ground wire to the sensor threads to stop the horn.
    Or there is a chance you could have picked up or created some air bubble for a short time, until the boat slowed down, possibly due to the brass water pump impeller Housing could be failing do to deep grooves inside housing creating a disturbance with the water flow.

    Constant beep alarms are for:
    1.) low outdrive lube level.

    Two Alarm beeps every 60 seconds are for:
    1.) Faulty cam,
    2.) IAC,
    3.) MAP,
    4.) MAT,
    5.) knock sensors.
    6.) open/short in the engine cooling temp circuit
    7.) open/short in fuel injector wiring circuit,
    8.) open/short in oil PSI circuit,
    9.) open/short in exhaust manifold cooling temp circuit,
    10.) open/short in sea pump circuit,
    11.) open/short in throttle position circuit
    Last edited by DaleM; 05-13-2010 at 06:16 PM.
    "LindSea II"
    '04 340 Sundancer, 8.1 Horizons (Current)
    Gunpowder Cove, MD
    Previous
    '03 280 Sundancer, T5.0 B3s (Previous)

  4. #34
    Join Date
    Jun 2009
    Location
    Toronto, ON
    Boat
    Sea Ray
    Details
    380 DA 1999
    Engine(s)
    Mercruiser 7.4 MPI
    Posts
    8

    Re: Mercruiser 7.4 MPI Engine alarm

    Yes it definitely was the wire/ connector to the knock sensor; cutting the wire back, eliminating some frayed strand and reconnecting the connector has done the trick. This would have saved me a couple of thousand $ if detected early/ or some of these responses would have come a year ago.

    Hope that my nightmare has helped others.

    Henning

  5. #35
    Join Date
    Aug 2009
    Location
    Mt Airy, MD
    Boat
    Searay
    Details
    340 Sundancer
    Engine(s)
    Twin 8.1 Horizons
    Posts
    371

    Re: Mercruiser 7.4 MPI Engine alarm

    Henning, hopefully it benefits all :)
    "LindSea II"
    '04 340 Sundancer, 8.1 Horizons (Current)
    Gunpowder Cove, MD
    Previous
    '03 280 Sundancer, T5.0 B3s (Previous)

  6. #36
    Join Date
    May 2009
    Location
    New Orleans, Louisiana
    Boat
    Sea Ray
    Details
    2004 340 Sundancer, 2008 Yamaha VX1100 Jet Ski
    Engine(s)
    8.1 Horizons, V-Drives
    Posts
    1,501

    Re: Mercruiser 7.4 MPI Engine alarm

    Quote Originally Posted by hnorup View Post
    Yes it definitely was the wire/ connector to the knock sensor; cutting the wire back, eliminating some frayed strand and reconnecting the connector has done the trick. This would have saved me a couple of thousand $ if detected early/ or some of these responses would have come a year ago.

    Hope that my nightmare has helped others.

    Henning
    Dale, it screws in like a spark plug, then you connect the little clip to it.

    Make sure you have actual "Wire" under that insulation, cause like I said in the earlier post, the insulation pulled back a bit, and there was no wire connected to the clip. Good Luck
    Ah Haaa!!! The Kid remembers some things I'm a wheelchair selling, Strut and Shaft trashin, wanna be boater, but I'm learning.

    Henning, now pay attention when you go slightly above 3000-3200 rpm and see if you still alarm, if not, you have solved your problem my friend.
    Last edited by Kreole Kid; 05-14-2010 at 01:27 AM.

    Bruce
    2004 340 Sundancer Knot On Call
    8.1's V Drives
    Previous Boat,
    Chaparral 190SSI

  7. #37
    Join Date
    Aug 2009
    Location
    Mt Airy, MD
    Boat
    Searay
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    340 Sundancer
    Engine(s)
    Twin 8.1 Horizons
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    371

    Re: Mercruiser 7.4 MPI Engine alarm

    :)

    I'm going for the knock sensor tomorrow. Time to put this baby to rest!
    "LindSea II"
    '04 340 Sundancer, 8.1 Horizons (Current)
    Gunpowder Cove, MD
    Previous
    '03 280 Sundancer, T5.0 B3s (Previous)

  8. #38
    Join Date
    May 2008
    Location
    Phoenix, NY
    Boat
    Sea Ray
    Details
    1999 Sundancer 370 DA
    Engine(s)
    7.4 MPI Horizon V Drives
    Posts
    454

    Re: Mercruiser 7.4 MPI Engine alarm

    Were is that sensor located?
    Connie G
    1999 Sundancer 370 DA
    7.4L MAG MPI HORIZON

  9. #39
    Join Date
    Aug 2009
    Location
    Mt Airy, MD
    Boat
    Searay
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    340 Sundancer
    Engine(s)
    Twin 8.1 Horizons
    Posts
    371

    Re: Mercruiser 7.4 MPI Engine alarm

    On mine, it's on the port side of the engine not far below the exhaust manifold. You'll know it because the sensor is attached to the side of the block and there is about a 4" long cable extension that comes off of it. At the end of that extension is the connector that everyone talks about.

    In this diagram it's #37.
    http://www.mercruiserparts.com/Show_...cal+Components

    Scroll down to the part number and click on it - you'll get a picture of what I'm describing.
    Last edited by DaleM; 05-14-2010 at 12:45 PM.
    "LindSea II"
    '04 340 Sundancer, 8.1 Horizons (Current)
    Gunpowder Cove, MD
    Previous
    '03 280 Sundancer, T5.0 B3s (Previous)

  10. #40
    Join Date
    Aug 2009
    Location
    Mt Airy, MD
    Boat
    Searay
    Details
    340 Sundancer
    Engine(s)
    Twin 8.1 Horizons
    Posts
    371

    Re: Mercruiser 7.4 MPI Engine alarm

    Just thought of one thing - based on your signature your engines will be in your boat in reverse of mine so keep that in mind.
    "LindSea II"
    '04 340 Sundancer, 8.1 Horizons (Current)
    Gunpowder Cove, MD
    Previous
    '03 280 Sundancer, T5.0 B3s (Previous)

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