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  1. #1

    Default 2002 sea Ray 8.1

    I have an 8.1 mercruiser in a 360 and it run smooth up to 4000 rpm and then starts to surge...42-4400 rpm back to3900 and back and forth. After removing the vent for the gas tank it ran for a while and then started pulsing again.... Then after removing the gas cap while at wot ,the engine ran perfectly......we ran for an hour at 3400 rpm without any problems....after that we ran the motors for 3 hrs to travel down the lake....again after trying to go to wot , the motor started to pulse and surge again.......I have twice changed fuel separators and put in new plugs....any suggestions ???????? We had the motor scanned,but no problem codes came up....

  2. #2
    Join Date
    Sep 2010
    Location
    Jersey Shore
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    Default Re: 2002 sea Ray 8.1

    Post the serial number.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  3. #3

    Default Re: 2002 sea Ray 8.1

    0m027993

  4. #4

    Default Re: 2002 sea Ray 8.1

    Or the other motor is 0M027992, I appreciate any help you can give me !!
    Last edited by RonR; 07-10-2016 at 10:16 PM.

  5. #5
    Join Date
    Sep 2010
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    Default Re: 2002 sea Ray 8.1

    Put a fuel pressure gauge on the engine and see what the pressure is when the problem occurs.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  6. #6

    Default Re: 2002 sea Ray 8.1

    Quote Originally Posted by Docksidemarineservices View Post
    Put a fuel pressure gauge on the engine and see what the pressure is when the problem occurs.
    Thank you... Will do...just thought I,d mention that none of the other gauges falter at all, oil pressure stays up temp ,alt , just the tach goes back and forth,with the motor

  7. #7

    Default Re: 2002 sea Ray 8.1

    Ok, we put a pressure gauge on the fuel line and at first pressure was 36, then as we accelerated the pressure fluxuated from 30 down to 20 and back to 35 but never went back into the 40's. Went back to idle, accelerated slowly, the pressure stayed at 40 until we get to about 3200 rpm then ,the pressure starts fluxuating, engine goes into guardian and we have to back out of it ???????
    Last edited by RonR; 07-12-2016 at 10:08 AM.

  8. #8

    Default Re: 2002 sea Ray 8.1

    How do we check the low pressure pump....is it the small pump on the tank..and use the same pressure gauge????? Thank you RR
    Last edited by RonR; 07-12-2016 at 10:11 AM.

  9. #9
    Join Date
    Sep 2010
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    Default Re: 2002 sea Ray 8.1

    I would start buy checking for a fuel restriction. Start at the fuel tank. Pull the dip tube assembly and look for a blockage. Pull the fuel shut off solenoid and do the same. Follow the fuel line all the way to the engine and see if you have an inline strainer. Look at the attached photo.





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    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  10. #10

    Default Re: 2002 sea Ray 8.1

    Thank you will do and get back to you.......

  11. #11

    Default Re: 2002 sea Ray 8.1

    Quote Originally Posted by RonR View Post
    Thank you will do and get back to you.......
    There isn't anything blocking the fuel lines at the tank ???????minimal debris

  12. #12
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    6,764

    Default Re: 2002 sea Ray 8.1

    I'd also add to Chris' list these:

    * Anti-syphon valve corrode/not fully opening?
    * shutoff valves not fully open?
    * spin on filters not seated tight?
    * hose clamp loose?

    An air leak on the suction side is just as bad as a restriction in terms of impacting the fuel pump...

  13. #13
    Join Date
    Sep 2010
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    Default Re: 2002 sea Ray 8.1

    Quote Originally Posted by RonR View Post
    There isn't anything blocking the fuel lines at the tank ???????minimal debris


    What about the rest of the fuel delivery system.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  14. #14

    Default Re: 2002 sea Ray 8.1

    We don,t seem to find any restrictions on the fuel side ,either at the tank,or at the pump......was informed this has a pancake filter under the water seperator.....how do I access it.......its the only fuel thing left!!!!!

  15. #15
    Join Date
    Sep 2010
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    Jersey Shore
    Posts
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    Default Re: 2002 sea Ray 8.1

    According to your serial number you do not have a gen3 fuel cooler hence no "Pancake fuel filter".
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  16. #16

    Default Re: 2002 sea Ray 8.1

    With only 20-30psi on the high side pump...should I replace it???? I don'T want to start changing things and not solve the problem

  17. #17
    Join Date
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    Default Re: 2002 sea Ray 8.1

    Take a picture of your fuel module.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  18. #18

    Default Re: 2002 sea Ray 8.1

    Quote Originally Posted by Docksidemarineservices View Post
    Take a picture of your fuel module.
    Will do asap

  19. #19
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
    Posts
    2,571

    Default Re: 2002 sea Ray 8.1

    Are you still having problems with fuel filler cap off? Having things run OK after removing fuel filler cap usually points to a blocked fuel tank vent line.
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280
    1972 22ft Bristol
    Honda 7.5HP 4 stroke Long shaft

  20. #20

    Default Re: 2002 sea Ray 8.1

    Quote Originally Posted by sandkicker View Post
    Are you still having problems with fuel filler cap off? Having things run OK after removing fuel filler cap usually points to a blocked fuel tank vent line.
    After running the boat for a few hour ride the engine started acting up again.....removing the gas cap didn't seem to have any affect on it!!!!!!! Before we left for the trip.....pulling the gas cap let the engine run just fine..... We thought we had cleared the gas vent line?.....?

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