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Results 1 to 16 of 16
  1. #1
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "I have a 1984 Egg Harbor 33&#

    "I have a 1984 Egg Harbor 33' with original twin 454 inboards (1300 hours each) coupled to Borg-Warner 1.91:1 reduction gears. The port engine (which is right hand rotation with a gear driven cam shaft) has a moderate knocking noise similar to a “diesel knock”. The noise has been present since I have owed it (3 years) with 200 hours of operation and no change. It is present both in gear and out of gear and is most noticeable at idle and low RPMS. The noise is more of a knock than a tapping and has proved hard to isolate. Its does not appear to be coming from the lifters or push rods--the rocker covers were removed and it did not appear to be coming from the lifter valley.

    At engine RPM’s increase the relative level of the knock decreases as other engine machinery noise drowns it out. It does not reveal itself if the throttle is increased and then suddenly lowered like a rod knock would. Ignition timing was verified with inductive light at 12 degrees BTDC. Distributor and wires are new and advance is working; ignition system is solid state Davis Unified Ignition. Fuel is fresh stabilized 87 octane with water separators and appears good. Same fuel produces no noise from the other engine. Belts from all accessories were removed with no change in noise level. Plugs are new. Engine starts right up (better than the starboard engine, has good power, and generally runs very well). Carbs were rebuilt and swapped with no change. Fuel lines were also swapped to no effect. Oil pressure is steady at 40 PSI at idle 700 RPM and 65 at 3000 RPMS. I haven’t run it hard because of the noise but this spring I’m going to turn it up and see what happens. I realize a remanufactured long block may be in my future.

    Oil is clean 20W-50. A quart of Lucas Oil treatment had no noticeable effect. One local engine guy listened to it and thought it might be piston slap. He did not think it was rod bearings as the noise decreased with increased engine speed. I haven't noticed much improvement after its fully warmed up, though. I’m thinking a compression check may be in order and I may try to determine whether it occurs with every rotation of the crankshaft or ever other rotation, i.e. is it top end or bottom end noise. I replaced the drive damper but the old one didn’t seem to have any defects.

    Cam gear? Piston Slap? Carbon build up on piston crown? Main bearing? Connecting rod bearing? Wrist pin? What do the experts say?"

  2. #2
    guest's Avatar
    guest Guest

    Default "Had one like that once, ran f

    "Had one like that once, ran for years that way and I never did find the cause before selling it.

    Have you checked for loose flywheel?
    Fuel pump, distributor / oil pump / drive problem?
    Doubt this but timing set.
    I believe that 30w oil is what Mercury recomends in that engine. Seems the oil pressure is on the high side for a stock engine. (oil pump check valve not opening)"

  3. #3
    Join Date
    Jan 2009
    Location
    friendly , wv, usa
    Posts
    460

    Default i had a motor to do the same e

    i had a motor to do the same exact thing come to find out the flywheel was completely cracked around the bolt cercumfrance i would have never guessed it but when we were pulling the motor after 2weeks of the noise the flywheel fell out and hit my arm when i used a prybar to push on the motor

  4. #4
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default I recently replaced the drive

    I recently replaced the drive damper and had a pretty good look at the flywheel. It looked fine and it wasn't loose but to be perfectly honest I didn't give it a thorough inspection because it never occured to me. The distributor was changed and made no difference. The oil pump appears to work well based on the pressures it generates. The timing set could be involved as its one of the main differences between the motor with the noise and the one without it (gear vs. chain driven camshaft).

    I don't know. I'm hoping it behaves like Guest's engine. Made a knock but never made a problem...

  5. #5
    Join Date
    Mar 2009
    Location
    Lowell, MA
    Posts
    1,211

    Default "I agree could be issue with t

    "I agree could be issue with the flywheel (back of the engine) Could also be a light rod bearing wear issue, where the oil pressure is cushioning it a bit, time to put a mechanic stethescope to it.."

  6. #6
    Join Date
    Aug 2006
    Location
    SW Ohio, USA
    Posts
    10,293

    Default "Carbon build up on piston

    "Carbon build up on piston crown?"

    One would think that the knock would get louder over time w/more carbon builldup. It can't hurt to try a can of SEAFOAM; 1/2 in the oil and 1/2 thru the carb. Maintain RPMs so it won't stall as you pour it in slowly. Shut it off and let it sit o'night. Run it the next day.
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  7. #7
    Join Date
    May 2009
    Location
    Bellingham, WA, USA
    Posts
    3

    Default "Heres a couple of Ideas: Th

    "Heres a couple of Ideas:
    The crank to block clearance is really tight in a big block and if the Thrust side of the main bearing is worn out the crank will hit the block. Normally it will make noise at Idle only, as the crank will walk as the load increases. Try to pull the crank forward with a screwdriver under the dampner and see if it quites down for a bit. I have found that if you slap down the throttle from 2500 or so sometimes the crank will walk forward and shut up. Oh yeah, the thrust side of the bearing could be gone and not affect the oil presure.

    The other thing is gear lash; Noisy idle issues that go away with a little load is most always backlash in the transmissions. Noises telescope through engines and are often hard to isolate.

    Plus 12 degrees is too much for a big block unless you have pulled some timing off of the top end, make sure you have not much more than 28 degrees total advance. (our fuels arn't that great anymore)"

  8. #8
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "It is about time for a stethe

    "It is about time for a stethescope and while I am at it I will try to determine if the knock occurs every crank revolution or every other revolution by counting the knocks in relation to the timing light flashes.

    I did use some sea foam last year and quite bit of carbon came out. Didn't seem to help quiet things down much, though. (Seafoam treatment on the Onan genset did make it run a little smoother). May have to try it again on the big block. Can't hurt.

    It could well be transmission noise. I know its not the damper. Damn noise is hard to track.

    Timing is exactly the same as starboard side which doesn't have the knock. Also advancing or retarding the timing doesn't quiet it down, so I don't think that's it. I've run it hard for 30 minutes several times over the past few years and it hasn't gotten any worse. Produces more power than the other side at WOT, too.

    Maybe its nothing to speak of.

    Thanks for your help."

  9. #9

    Default "I have a 1992 Bayliner that h

    "I have a 1992 Bayliner that has the same issue with the port engine. It's a 305 and has an intermittent knock that is most noticeable at idle. I've ruled out rod and crank bearings because the the frequency doesn't change when the RPM's are increased. I also thought it might be the oil pressure bypass valve but I'm getting good flow to the filter. Seems to be coming from the left bank of cylinders, I can feel the knock more on the left exhaust elbow than the right. My next check is the exhaust butterfly valves, if they're rusted shut it might be causing excessive exhaust back pressure. I'll monitor this post and share anything I find."

  10. #10
    Join Date
    Jan 2009
    Location
    friendly , wv, usa
    Posts
    460

    Default Thomas I think you hit the na

    Thomas I think you hit the nail on the head when you said transmission. I worked on a ferry boat in the late 80s on the weekend and i would go to the engine house and hear this knocking noise all the time and i was in the pilot house and ask the pilot what the knocking was and he said some type of coupler in the transmission. anyways that same ferry is in operation today with the same knock

  11. #11
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "I have found that tracking d

    "I have found that tracking down the source of engine noises is pretty tough. You need a trained ear, an engine stethoscope, some skill, and maybe a little luck to go along with it.

    Carl: Excessive exhaust back pressue will cause backfiring through the carb., a sympton that thankfully I do not have.

    Steve: After the drive damper was replaced the noise seemed to "improve" but it is not completely gone. It also seems worse at start up than after the engine is completely warm; before the damper replacement there was no noticeable difference warm or cold, so the behavior seems a little different. I have not had a chance to run it up above 1200 RPMS yet, so I haven't experienced the full range of operating conditions. There is a suggestion that the knock is still there but somewhat improved by the damper replacment. I do not have a defintive answer but I plan to very soon.

    If it gives up its life, so be it. I can’t keep trying to fix something when I'm not 100% sure what I’m “fixing”.

    The engine starts and runs well and produces good power. That's about all I can expect from a 25 year old engine, and I probably should be happy to have it that way.

    Best wishes,

    Major Tom"

  12. #12
    Join Date
    Jan 2009
    Location
    friendly , wv, usa
    Posts
    460

    Default well best of luck finding it a

    well best of luck finding it and if all else fails take the oil pan off and take the hammer away from the squirel lol just some humor

  13. #13
    Join Date
    Sep 2006
    Location
    Coquitlam, British Columbia, Canada
    Posts
    193

    Default "Once had a motor knock that t

    "Once had a motor knock that turned out to be an undersized piston.The hotter the motor ran, the less it knocked as the piston expanded. Never could hear it when driving, only at an idle. Pulled plug wire to locate guilty cylinder, changed out that piston, noise gone. Was told by more than one mechanic that it would probably run like that for a long time but it bugged me. Just throwing out another idea for you !!"

  14. #14
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "Yup Barry, could very well be

    "Yup Barry, could very well be piston slap from an undersized piston and/or undersized piston skirt. If so, it will most probably live for a long time. Last night I listened to it from a cold start until it was fully warm and the knock improved considerably as it warmed up. It also becomes much less noticeable at higher RPMS both in neutral and in gear underway. Its time to run it hard and see what happens... Its been this way for 4 years and about 300 hours. Maybe it will live another year, or several more years, for that matter."

  15. #15
    Join Date
    Jan 2009
    Location
    friendly , wv, usa
    Posts
    460

    Default Tom i think Barry may be on to

    Tom i think Barry may be on to something. makes perfect sense

  16. #16
    Join Date
    Jan 2008
    Location
    Groveland, MA, USA
    Posts
    139

    Default "I agree, Steve. Knock from a

    "I agree, Steve. Knock from an undersized piston is consistent with all of the enngine's symptoms and behavior. The only other explanation that kind of fit was the drive damper, and I changed that."

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