Ongoing 8.1 Issue Still Unresolved

Discussion in 'General Discussion' started by copb8tx, Dec 6, 2017.

  1. hottoddie

    hottoddie Member

    953
    Jan 11, 2012
    Boston/Cape Cod
    1986 Sea Ray 390 Express
    Garmin 4212 Chartplotter
    Garmin 24 HD Radar
    Garmin GSD 22 Sounder
    Garm
    454 Crusaders
    Instead of removing all 8 coils from the other motor why not just remove 1 and replace one coil at a time to see the misfire goes away. If it does you know which coils is bad. If it doesn't go away then you only have one coil to reinstall back on the other motor. BTW use dialectric grease on the connections.
     
  2. copb8tx

    copb8tx Active Member SILVER Sponsor

    Jan 26, 2008
    Lake Texoma, TX
    2005 420 Sundancer
    T-8.1S Horizons
    It seems I should just see if my marina can put a scan tool on it, run it and see if there any codes that will narrow it down?
     
  3. copb8tx

    copb8tx Active Member SILVER Sponsor

    Jan 26, 2008
    Lake Texoma, TX
    2005 420 Sundancer
    T-8.1S Horizons
    Only problem with this is that you have take the boat out and run it between each coil. That's going to take a lot of time and make that engine compartment smoking hot!
     
  4. Espos4

    Espos4 Member

    198
    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    This is the reason to swap all 8 at once.
    One trip will tell you if a coil(s) are the issue.
     
  5. scoflaw

    scoflaw Active Member SILVER Sponsor

    Aug 10, 2011
    cape cod mass
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    It's never the coils
     
  6. copb8tx

    copb8tx Active Member SILVER Sponsor

    Jan 26, 2008
    Lake Texoma, TX
    2005 420 Sundancer
    T-8.1S Horizons
    Scheduled a meeting with a tech next Tuesday to take him out for a spin and run the codes. Figured I've passed my level of usefulness on this and need to stop chasing my tail.

    I'll post back when I know more.
     
  7. MickT

    MickT Member

    40
    Aug 5, 2016
    australia - newcastle
    2006 sundancer 300
    twin mercruiser 5.0 mpi w/bravo III
    First thing that comes to my mind when you say heavy load, large throttle opening and "popping" noise is "pinking" or "pinging", which is uncontrolled detonation of the fuel air mixture, usually caused by either substandard fuel, excess compression, a lean mixture, or very advanced ignition timing.

    Before you tear down parts of the engine, first you need to confirm the kind of fault - step one, get the fault history downloaded from the ECU and examined by someone who knows what they are looking at.
     
  8. Jetgod

    Jetgod Member

    149
    Dec 14, 2012
    Victoria,BC
    310 Sundancer 2000
    5.7 Mag MPI V-drives
    CHECK THE COMPRESSION. i HAVE CHASED AROUND ALL KINDS OF ISSUES AND ALWAYS FOUND OUT THE COMPRESSION WAS OFF IN THE END.nOW , WHEN i HAVE AN ISSUE i CHECK PLUGS AND WHILE THEY ARE OUT,CHECK THE COMPRESSION.
     
  9. PlayDate

    PlayDate Well-Known Member SILVER Sponsor

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers

    This is the right course.

    You have already chased the simple things. Hopefully the scanner will provide a clue or clues if it is a part to be replaced.

    Depending on the engine hours it seems you might have an intake valve not sealing at higher rpms. That would create a popping sound at higher rpms. Typically electrical issues like coils/wires/plugs fit into the loss of power world. Rhythmic noises on the other hand tend to be mechanical. It could be something as simple as a broken valve spring or a sticking guide.

    Hopefully he can narrow it down.
     
  10. techmitch

    techmitch Active Member SILVER Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    M Prod likes this.
  11. M Prod

    M Prod Member SILVER Sponsor GOLD Sponsor

    132
    Oct 6, 2017
    North Vancouver, BC
    2005 340 Sundancer
    Aquapro Dinghy w/ Honda 8hp
    Kohler 5KW Genny
    Raymarine C80
    8.1 Horizons /V Drives
    X1000
     
  12. hottoddie

    hottoddie Member

    953
    Jan 11, 2012
    Boston/Cape Cod
    1986 Sea Ray 390 Express
    Garmin 4212 Chartplotter
    Garmin 24 HD Radar
    Garmin GSD 22 Sounder
    Garm
    454 Crusaders
    I remember in the "OLD DAYS" we would replace valve stem seals on an engine by using compressed air in the cylinder to hold the valve in place while using a valve spring compressor to remove the springs and replace the seal. I would think the same procedure could be used to replace a broken valve spring in a marine engine without having to remove the heads and doing a complete top end overhaul.
     
    Jetgod likes this.
  13. PlayDate

    PlayDate Well-Known Member SILVER Sponsor

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    You still can....the only problem is as we have gotten older and wiser.....we realize that finding one problem usually means there are more waiting to be found.

    I had client who said he had a "lifter noise". We pulled the valve cover and found a bent push rod. The owner just wanted to replace the push rod. Well, something bent the push rod and would in all likelihood would bend the new one. A bore-scope showed the piston had come in contact with the valve. In the end....the guides were shot from poor maintenance (never changing the oil) and the heads had to be rebuilt.
     
  14. techmitch

    techmitch Active Member SILVER Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    The old days were when we many times we didn't have compressed air and you would put the piston at BDC and feed a piece of rope into the cylinder then slowly brought the piston up to hold the valves up to complete the job.
     
    Espos4 likes this.
  15. Sublimetime

    Sublimetime Member

    377
    Oct 22, 2007
    clifton nj
    420 da
    454
    MY GUESS

    Popping at higher rpm indicates a INTAKE valve not seating, allowing the explosion created at the next stroke to be heard back out through the intake manifold and throttle body, bent pushrod, broken valve spring, dirty valve stem, loose or missing keepers, bad/gummed up lifter, broken or loose valve seat.
     
  16. Korkie

    Korkie Member

    98
    Feb 2, 2016
    Breton Bay, MD
    2006 Sundancer 340 / 496 Mags Bravo III Drives
    Merc 496 Mags, Bravo 3 Drives
    Have you put this motor on a computer yet? I chased around a similar intermittent issue for a year, spend $1000 bucks changing this -that and the other. Finally, had it put on the computer. Took the tech 15 minutes total to find the problem and fix it. Ended up being a loose pin in the harness. He repaired the pin and charged me a total of $150.00. Money well spent as he also did the other motor and found a small ignition issue as well and repaired that. All for the $150.00
     
  17. copb8tx

    copb8tx Active Member SILVER Sponsor

    Jan 26, 2008
    Lake Texoma, TX
    2005 420 Sundancer
    T-8.1S Horizons
    Engine has 420 hours on it. Oil changed every year, even the flood year when I only put 4 hours on the boat. Just put 3rd set of plugs in it since I've owned it the last 7.5 years. Freshwater lake boat that is typically cruised at 3400-3500rpms to a destination 3 to 10 miles away. In other words it's had a easy life.

    Hopefully we'll know a lot more tomorrow after it's had the codes read. Obviously praying for something simple but whatever it is I just look forward to having a more clear plan of action.

    What are your guys thought that it could be a faulty throttle position sensor. My very mechanically inclined friend bet me a case of beer that the TPS is bad. I really hope I owe him some beer.
     
  18. copb8tx

    copb8tx Active Member SILVER Sponsor

    Jan 26, 2008
    Lake Texoma, TX
    2005 420 Sundancer
    T-8.1S Horizons
    So good news today. Tech said that the #5 ignition coil pack shows to be throwing a fault code intermittently. He's pretty sure that's the issue. We took the boat out and ran it through its paces and he said he's positive it's not a mechanical issue and that is either fuel or fire.

    Only other option he feels it could be is the fuel pump system that has a Mercruiser TSB out on it for flaking paint.

    So I've got my fingers crossed he's right and will wait for the final fix.

    Thanks all!
     
    Last edited: Dec 12, 2017
  19. Espos4

    Espos4 Member

    198
    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Thanks for the update.
    Hope this is resolved quickly.
     
  20. techmitch

    techmitch Active Member SILVER Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    A code for cylinder misfire or coil circuit (primary/secondary) code?
     

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