Logo
Get instant online access to repair manuals for your Mercury / Mariner outboard. Online Manuals
MercuryMariner
Order printed Mercury / Mariner service manuals — shipped to your door! Printed Manuals
MercuryMariner
Use engine diagrams to find & order parts for your Mercury / Mariner engine. Engine Diagrams
MercuryMariner
Find parts quickly with Mercury application guides. Quick Parts Guide
MercurySierraCDI
Results 1 to 11 of 11
  1. #1

    Default rough running 200 hp 1996 mariner

    Greetings all.
    I continue to have a rough running, hard to idle 200 hp mariner 2 cycle fuel injected. It fires and runs rough when cold but after a few minutes it get hard to start with extremely low idle. Dies when I put it in gear. It seems to run ok once I get it up and running across the lake. I have recently ran it out of gas
    Repairs/ parts I have replaced include:
    1. 6 coil packs
    2. switch blocks (2) Sierra
    3. spark plugs
    4. complete fuel line & cleaned the tank
    5. Compression test: 3 @ 135, [email protected]
    6. primary fuel pump diaphragm(s)
    7. The existing injection fuel pump has 23 lb, 20 second time-out with ignition on.
    8. All cylinders a firing with bright white spark and are consistent.
    9. I confirmed the fuel oil mix by color against a known 50:1 mix in identical glass jars. Quicksilver oil & non-ethanal 91 octane gas

    I am now leaning towards a fuel inject regulator. Does anyone know how to test the regulator or is there something else I should be testing?
    Thanks for your help.

  2. #2
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    5,484

    Default Re: rough running 200 hp 1996 mariner

    Fuel pressure too low....
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  3. #3

    Default Re: rough running 200 hp 1996 mariner

    OK. I read that 80 lbs was a good pressure somewhere. I will change the electric fuel pump in the injection body and let you know how it turns out. Thanks

  4. #4

    Default Re: rough running 200 hp 1996 mariner

    A little research showed me that actually the fuel pressure was a consistent 35. The running voltage was 7.5 & 19. That seems really high for the charging system. The boat ran rough and smoked quite a bit and would not idle

  5. #5
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    5,484

    Default Re: rough running 200 hp 1996 mariner

    Naa...you need 36+psi. Also check spark at idle running with timing light as sounds like you got a stator problem to one bank.
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  6. #6

    Default Re: rough running 200 hp 1996 mariner

    Ok
    I will check the consistency of the spark while high idle. 1200 rpms. any lower and it will stall. Do you suggest I change the fuel pump anyway. I am not against changing to new parts. I keep a good log book of new parts.

  7. #7

    Default Re: rough running 200 hp 1996 mariner

    I was able to check the spark and it appeared very weak. 1/16" arc on all cylinders. Shouldn't this spark be scary strong? I checked all cylinders and didn't get bit once.
    Have I thanked you for your help? Thank you

  8. #8
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    5,484

    Default Re: rough running 200 hp 1996 mariner

    Should jump a min 3/8 air gap easily...blue with a pop
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  9. #9

    Default Re: rough running 200 hp 1996 mariner

    I replaced 6 coil packs with new ones. What else would cause a weak spark. I am still concerned about the 19V & 7V reading I had on the fuel pump while the engine was running. Does this all point back to the rectifier? Could this 19V have impacted the new switch blocks?

  10. #10
    Join Date
    Nov 2011
    Location
    tennessee
    Posts
    5,484

    Default Re: rough running 200 hp 1996 mariner

    Stator charges capacitor in switchbox which dumps to coils. Check DVA output on stator
    Pappys Sales and Service
    Owner and Factory Certified Technician
    Former racer KDBA (Kentucky Drag Boat Association)

  11. #11

    Default Re: rough running 200 hp 1996 mariner

    That sounds like great advice. So if the voltage signal from the switch box is weak then the output of the coils will also be weak? I have ordered a new rectifier/regulator due to the high (19v) supply to the fuel pump ($30). It looks like the 16-19 amp stator is around $150 new. I may just change it and start anew with the ignition system.

Similar Threads

  1. 1996 mercury bigfoot 50elpt4s running rough
    By Danny Wheeler in forum Mercury Mariner Outboard Forum
    Replies: 4
    Last Post: 06-24-2022, 03:16 AM
  2. Mariner 175 running rough
    By surreyboy in forum Mercury Mariner Outboard Forum
    Replies: 2
    Last Post: 01-09-2019, 10:14 AM
  3. Mariner 25 running rough
    By bastormer in forum Mercury Mariner Outboard Forum
    Replies: 5
    Last Post: 05-14-2012, 10:32 AM
  4. 1996 Mariner 90 HP Rough Idle
    By gwfiii in forum Mercury Mariner Outboard Archive
    Replies: 10
    Last Post: 05-21-2009, 11:31 AM
  5. 1996 Mercury Mariner 125hp rough idle
    By cha_cha in forum Mercury Mariner Outboard Archive
    Replies: 3
    Last Post: 04-10-2007, 05:51 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •