Clanking/banging noise, #5 Zero Compression

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by frank2644, Jul 22, 2019.

  1. frank2644

    frank2644 Member

    77
    Aug 16, 2008
    Long Island, NY
    270 Sundancer 1995
    454 Mercruiser Bravo II
    After a 20 minute trip, with the engine running great, and then slow trolling around my destination for a couple of minutes my engine suddenly died. Upon restart it made a horrible fast clanking/banging noise and I shut it down immediately. Got towed back to home slip.

    Upon inspection, # 5 spark plug gap was bent closed and i/2 of the ceramic insulator is missing, like something hit it. #5 cylinder also has zero compression. #3 has about 90 lbs, while other cylinders 115-138 lbs. Inspection camera shows one of the #5 valves sitting maybe 1/8" deeper into the head than any other valve, making me think the valve seat is missing. No apparent damage to piston or cylinder walls and no metal pieces in view. The piston seems to go up and down normally. Pulled both valve covers and everything looks clean and seems to be operating normally while cranking.

    Wild guess: somehow the valve seat broke free and hit the spark plug, then the pieces were blown out through the exhaust. I put a new plug in and started the engine, the horrible clanking/banging noise caused an immediate impulse to shut it down and I did. The new plug doesn’t show any damage. Adjusted the clearance on the recessed valve...no difference in sound.

    I have been around engines and heard rod knocks, lifter noises, etc. Usually those noises are not terribly loud and sometimes related to engine RPM and not terribly concerning. However, the noise from my engine, leaves little doubt that something bad is happening and causes an immediate knee-jerk reaction to shut the engine down. The noise is pretty fast, giving the impression that it’s not related to happenings in any one cylinder or valve. And the sound is not very dull or deep sounding and has a clanky aspect. It’s hard to describe. Although, my impression of the sound may be distorted given that the hard starting requires pretty high throttle opening and high rpms upon startup.

    I have to believe that noise is related to the spark plug damage but I can’t figure out what it is. Any suggestions as to what could be causing that noise?

    Thanks,
    Frank
     
  2. Creekwood

    Creekwood Well-Known Member GOLD Sponsor

    Apr 26, 2009
    Oakville and Georgian Bay, Ontario
    '97 330 Sundancer, Raymarine C80 suite with radar, Mercury 310 Hypalon w/8hp Yammie 2stk
    2X 454 carbs w/ vDrives
    Sounds like you should pull the heads and see what is going on.
     
    Snapon24 and Espos4 like this.
  3. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Yup, no choice as a starting point
     
    Espos4 likes this.
  4. Wanderer 290

    Wanderer 290 Active Member

    122
    Jul 1, 2019
    01 sea ray 290 sundancer
    Twin 5.7 b3’s
    What engine, how many hours? Etc.
    From the factory the valve seats are just heat treated head casting material. Actual valve seats are usually a sign the head has been reconditioned.

    Description sounds like a fractured valve but just a guess?
     
  5. cfd95

    cfd95 Member

    327
    Nov 5, 2013
    Northport Long Island
    2002 310 Sundancer
    350 Horizons
    V Drives
    #3 and #5 center cylinders under the riser
    probably have bad riser or gaskets leaking water into cylinders
     
  6. Wanderer 290

    Wanderer 290 Active Member

    122
    Jul 1, 2019
    01 sea ray 290 sundancer
    Twin 5.7 b3’s
    Agreed definitely a possibility!
     
  7. frank2644

    frank2644 Member

    77
    Aug 16, 2008
    Long Island, NY
    270 Sundancer 1995
    454 Mercruiser Bravo II
    Thanks, everyone for the help. I'll respond to the comments and suggestions below:

    1.It's a 1995 Merc 454 Gen 5 Bravo II, with less than 900 hours. I doubt a valve job was ever done, but could be.

    2. True, the valve seats may not be a separable part, but the valve does seem to be countersunk into the head uniformly (not crooked, etc.). Like I imagine would happen if there was a missing seat.

    3. Can't see the whole valve, could be cracked but hard to believe that would explain the nasty noise.

    4. Interesting point that #3 & #5 are under the riser. Although #5 was historically low, about 70 lbs 2 years ago, but it ran great. Risers and manifolds and flappers were replaced last year with OEM parts, although maybe the install was bad and leaked. But there was no sign of rust, water, steam, or overheating.

    5. Pulling the head probably means hauling it home first, if the block then turns out to be bad it'll have to be hauled again to the shop. About $250-$350 each way. Might be doable in the water, I'll have to think about that.

    At this point I'm wondering if i should start it and resist shutting it down immediately. Instead wait for it to idle down and assess the noise, oil pressure, etc. then. Maybe the unburned gas due to the excessive cranking needed to start it is contributing to the noise.

    I’d love to hear further comments, so far they have been very interesting.

    Thanks, again,
    Frank
     
  8. Ididntdoit

    Ididntdoit Well-Known Member

    Dec 5, 2007
    New England & South Florida
    Boatless
    Boatless
    at 70lbs that cylinder has been bad for awhile....my vote is detonation - the valve is likely tuliped - this would explain the damaged plug as well.....dont bother starting it - the quicker you pull the heads, the quicker you can get back to boating
     
  9. Ididntdoit

    Ididntdoit Well-Known Member

    Dec 5, 2007
    New England & South Florida
    Boatless
    Boatless
    ......
     
  10. Wanderer 290

    Wanderer 290 Active Member

    122
    Jul 1, 2019
    01 sea ray 290 sundancer
    Twin 5.7 b3’s
    There are internal problems that necessitate removing the heads. Based on what’s revealed I suspect you may be in to a major rebuild,
    Hope for the best though!
     
  11. capecodcruiser

    capecodcruiser Member

    450
    Aug 1, 2008
    Falmouth, MA
    2001 310, 350 HO's/Vdrives.
    Mercruiser MPI 350 HO's
    Don't waste time trying to do any more diagnostics. You have done what you need to. 0PSI is 0PSI. The cause will reveal itself once you pull the head. Please keep us posted.
     
  12. Thornton69

    Thornton69 Active Member

    462
    Sep 15, 2014
    Northern BC
    1981 245 SDC
    1984 18' Valco sled
    5.7 260 Merc/ Bravo 2
    Evanrude 115/80 jet
    I would pull the oil filter first. No point fighting with the heads if the whole engine has to come out.
     
    Rusted Nut likes this.
  13. joeyleggz

    joeyleggz Active Member

    532
    Jan 15, 2013
    long island
    current boat: 1997 sea ray 330 express cruiser
    twin 454's efi
    Yup sounds like a tuliped valve definitely a valve train issue high-speed clickety-clackety ,do not start it again cylinder three and five sitting Under the riser are notorious for water reversion and misting and rusting out If you had 70 psi a few years ago the nail was in the coffin then Sorry brother good luck
     
  14. frank2644

    frank2644 Member

    77
    Aug 16, 2008
    Long Island, NY
    270 Sundancer 1995
    454 Mercruiser Bravo II
    Wow, more great comments. Thanks everyone.

    At this point I'm sure that the valves are shot and, although likely, it's not certain that the engine is shot.

    Because the camera seems to show that the cylinders and piston are okay, and the failure happened after several minutes of low speed operation without noise, smoke, etc., it's plausible that the horrible noise is "detonation". (I think that means unburnt fuel combustion in the manifolds).

    I have quotes in the $2000 area to get a valve job done by a shop. To do it myself, I'd probably have to haul it home, at a hauler cost of about $800 round trip. Head rebuilds by a Machine shop, gaskets, and misc parts, total cost maybe another $800.

    A rebuilt Jasper engine goes for about $7k installed with a two year warranty.

    One possible action is just to rebuild one head while in the water. I'm guessing maybe $500.

    It would really help me decide if I could confirm the detonation theory. Maybe I could remove the pushrods on the zero cylinder and see if the horrible noise disappears. Any harm trying that? Maybe just remove the intake pushrod?

    Thanks, again,
    Frank
     
  15. joeyleggz

    joeyleggz Active Member

    532
    Jan 15, 2013
    long island
    current boat: 1997 sea ray 330 express cruiser
    twin 454's efi
    Best of luck to you ,tearing it down is going to show what’s wrong otherwise you’re just playing guessing games it still Has to be taken apart ,I was looking at a valve job myself but once I started tearing things apart and saw that the exhaust ports where they mate it up to the exhaust manifold we’re not looking too kosher , I had the same story as you coming off a high-speed run going slow and idling engine just stopped went to restart it sounded like 1000 marbles rolling around in there, shut her down immediately did exactly what you did came up with zero compression in cylinder three I did the borescope thing too I did a leak down test realize that it was the valves that were no good in two cylinders and you can see the seat material was blown all over the cylinders so therefore some of it was melted into the top of the piston and who knows if any little chips got down the side where the rings are once I took it apart i saw that there was more to it than that so I went with fresh motors on both sides because I really liked the boat
     
  16. Wanderer 290

    Wanderer 290 Active Member

    122
    Jul 1, 2019
    01 sea ray 290 sundancer
    Twin 5.7 b3’s
    Just something to consider.... A boat engine is solidly mounted vs an auto engine that has vibration absorbing mounts. Mis-fire creates significant vibration and may cause damage to the vessel and the engine mounts.
     
  17. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    I would NOT recommend that.

    The pushrods keep the lifters in place. Running the engine without a pushrod could allow the lifter to be pushed out of its bore, then you’d lose oil pressure to the entire engine, damaging the crank and rod bearings.
     
    PlayDate likes this.
  18. frank2644

    frank2644 Member

    77
    Aug 16, 2008
    Long Island, NY
    270 Sundancer 1995
    454 Mercruiser Bravo II
    Espos4,
    True, losing oil pressure is not a good thing, but I'm only thinking about running it for maybe 10 seconds to see if that horrible clanking disappears. Given that the engine is likely bad anyway, I'm not risking much.

    Of course, if removing the pushrods is not likely to produce meaningful results, I would like to know that. And I'm hoping if that's the case someone here will comment.

    In summary, it seems to me that if pushrod removal reduces the clanking noise significantly, that would be meaningful. That is, it would strongly suggest that noise is a direct result of bad valves and not due to some serious malfunction in the block.

    Thank you,
    Frank
     
  19. Creekwood

    Creekwood Well-Known Member GOLD Sponsor

    Apr 26, 2009
    Oakville and Georgian Bay, Ontario
    '97 330 Sundancer, Raymarine C80 suite with radar, Mercury 310 Hypalon w/8hp Yammie 2stk
    2X 454 carbs w/ vDrives
    To be honest this is a ridiculous conversation. You have some form of mechanical damage issue that cannot be fixed without taking the heads off at a bare minimum. Running the engine to diagnose it will not do any good at all and may do significant harm. Just take it apart or have someone do it for you.
     
  20. frank2644

    frank2644 Member

    77
    Aug 16, 2008
    Long Island, NY
    270 Sundancer 1995
    454 Mercruiser Bravo II
    To me, it seems highly unlikely that it's worth the expense of removing the heads considering repair shop costs, hauling, etc. given the age of the engine.

    I still think removing the pushrods might provide valuable insight and would like to hear more pro's and con's.

    Thanks for your input.
    Frank
     

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