Help a boater diagnose a 496 Mag issue....
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Help a boater diagnose a 496 Mag issue....

  1. #1
    Rubbing is Racing!! Cole Trickle's Avatar
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    Default Help a boater diagnose a 496 Mag issue....

    496 Mag Issue


    Looking for some opinions on what might be wrong with the 496 Mag in our boat.

    On our very last trip out last season the engine developed an issue where it would start but have limited power when it was cold. Once it reached normal operating temp (160) it would run fine. The engine almost behaved like it was flooded. Even with full throttle it didn't have enough power to even get on plane, until it came up to operating temp.

    So I had it in for service over the winter. The repair shop checked the plugs, alternator voltage, and replaced the fuel filter. No codes were set or pending. According to them it ran fine on the hose. About a month later we attempted to use the boat and once again it did the exact same thing, except this time the problem did not go away after the engine came up to normal operating temp. I could smell strong gas fumes and the boat barely made it back to the trailer. This issue has definitely gotten worse.

    Any suggestions?

    http://www.performanceboats.com//showthread.php?t=37171


    Thanks.

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  3. #2
    Hub Cap Annie & Wheel pvhca's Avatar
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    Quote Originally Posted by Cole Trickle View Post
    496 Mag Issue


    Looking for some opinions on what might be wrong with the 496 Mag in our boat.

    On our very last trip out last season the engine developed an issue where it would start but have limited power when it was cold. Once it reached normal operating temp (160) it would run fine. The engine almost behaved like it was flooded. Even with full throttle it didn't have enough power to even get on plane, until it came up to operating temp.

    So I had it in for service over the winter. The repair shop checked the plugs, alternator voltage, and replaced the fuel filter. No codes were set or pending. According to them it ran fine on the hose. About a month later we attempted to use the boat and once again it did the exact same thing, except this time the problem did not go away after the engine came up to normal operating temp. I could smell strong gas fumes and the boat barely made it back to the trailer. This issue has definitely gotten worse.

    Any suggestions?

    http://www.performanceboats.com//showthread.php?t=37171


    Thanks.
    Sell it!! JK. I have no clue just thought I'd throw that out. Kinda weird that no codes are popping up. Good Luck!!

  4. #3
    Ultra26 # 1
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    Quote Originally Posted by Cole Trickle View Post
    496 Mag Issue


    Looking for some opinions on what might be wrong with the 496 Mag in our boat.

    On our very last trip out last season the engine developed an issue where it would start but have limited power when it was cold. Once it reached normal operating temp (160) it would run fine. The engine almost behaved like it was flooded. Even with full throttle it didn't have enough power to even get on plane, until it came up to operating temp.

    So I had it in for service over the winter. The repair shop checked the plugs, alternator voltage, and replaced the fuel filter. No codes were set or pending. According to them it ran fine on the hose. About a month later we attempted to use the boat and once again it did the exact same thing, except this time the problem did not go away after the engine came up to normal operating temp. I could smell strong gas fumes and the boat barely made it back to the trailer. This issue has definitely gotten worse.

    Any suggestions?

    http://www.performanceboats.com//showthread.php?t=37171


    Thanks.
    Fuel pressure regulator ???

  5. #4
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    sounds like a fuel issue to me as well...regulator, injector etc

  6. #5
    Senior Member havasu1's Avatar
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    You may want to check out you fuel lines. I had a friend with a similar issue and the fuel lines were deteriorating and collapsing. Reduce flow.

  7. #6
    MEDIUM PIMPIN!!! ~NORD~'s Avatar
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    Fuel lines or filter or fuel water seperator..........

  8. #7
    Senior Member PLACECRAFT20's Avatar
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    What model is the motor? Have you put a pressure guage on the fuel rail to check it? Will it clean out in neutral? and last but not least do you have a scan tool or access to one? It could possibly be that the temp sensor is bad but without a scan tool you are shooting in the dark. The guage uses a different sender than the computer.

  9. #8
    Rubbing is Racing!! Cole Trickle's Avatar
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    Quote Originally Posted by PLACECRAFT20 View Post
    What model is the motor? Have you put a pressure guage on the fuel rail to check it? Will it clean out in neutral? and last but not least do you have a scan tool or access to one? It could possibly be that the temp sensor is bad but without a scan tool you are shooting in the dark. The guage uses a different sender than the computer.
    03 Merc 496 Mag

  10. #9
    Senior Member EdonShano's Avatar
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    Quote Originally Posted by Cole Trickle View Post
    496 Mag Issue


    Looking for some opinions on what might be wrong with the 496 Mag in our boat.

    On our very last trip out last season the engine developed an issue where it would start but have limited power when it was cold. Once it reached normal operating temp (160) it would run fine. The engine almost behaved like it was flooded. Even with full throttle it didn't have enough power to even get on plane, until it came up to operating temp.

    So I had it in for service over the winter. The repair shop checked the plugs, alternator voltage, and replaced the fuel filter. No codes were set or pending. According to them it ran fine on the hose. About a month later we attempted to use the boat and once again it did the exact same thing, except this time the problem did not go away after the engine came up to normal operating temp. I could smell strong gas fumes and the boat barely made it back to the trailer. This issue has definitely gotten worse.

    Any suggestions?

    http://www.performanceboats.com//showthread.php?t=37171


    Thanks.
    buy my HO..you'll be better off..

  11. #10
    AKA Janda HpLavey's Avatar
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    Do you have mufflers? Maybe there clogged. If not I think its a fuel issue.
    Pump, seperator, hose. If it was an injector it woud'nt run smooth.

    Good luck!


  12. #11
    Rubbing is Racing!! Cole Trickle's Avatar
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    Quote Originally Posted by Unforgiven View Post
    buy my HO..you'll be better off..
    Not my boat I already have a 120 hour HO that dosen't get used in my 05 Sleek.

    They have zero desire or need for a new motor

  13. #12
    Senior Member PLACECRAFT20's Avatar
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    I have the 03 manual at my shop that I will look at tonight. Do you have access to a scan tool?

  14. #13
    AKA Janda HpLavey's Avatar
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    Oh
    I just thought of this
    I think its a coil


  15. #14
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    had the same problem,496 mag took it to one shop in havasu and they replaced the computer $1400.00. told me it ran fine.put it in the water and problem still thier.in the shop three times in one year no luck.
    took it over to Alco Marine and they pulled all the injectors out and found two bad and the rest clogged.problem solved. $350.00
    needless to say i don't go to my regular shop any more

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