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11-29-2018, 05:52 PM
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#1
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Member
City: Pensacola
Join Date: Nov 2018
Posts: 7
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Knocking
Got a knocking in my port Ford Lehman 120. Injector? Any thoughts or advice. Just finished 800 mile trip.
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11-29-2018, 06:30 PM
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#2
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Enigma
City: Slicker?
Join Date: Oct 2007
Posts: 16,566
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Greetings,
Welcome aboard. Sorry, I'm not a mechanic although we do have 120 Lehmans. I wouldn't recognize knocking if it bit me on the foot. Best wishes.
__________________
RTF
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11-29-2018, 06:38 PM
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#3
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Senior Member
City: Out and About
Vessel Model: Sold-GB 52 Europa, Queenship 59, Tolly 45
Join Date: Nov 2016
Posts: 484
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Any smoke?
You can determine which cylinder causes the knock by loosening injector fuel lines one at a time. If the knock goes away when you loosen a particular fuel line, you have identified the cylinder. Knocks can be caused by injectors, bearings, pistons, valves, etc.
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11-29-2018, 06:55 PM
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#4
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Senior Member
City: North NJ
Vessel Name: Bassey
Vessel Model: 17' Bass
Join Date: Aug 2016
Posts: 438
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Or a infrared gun to the exhaust manifold to determine which is colder if you are having a dead cylinder.
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11-29-2018, 09:55 PM
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#5
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Guru
City: Gibsons, B.C., Canada
Vessel Name: Island Pride
Vessel Model: Palmer 32'
Join Date: Oct 2007
Posts: 4,414
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A knock can also be caused by a faulty injector which feeds too much fuel or at the wrong time due to the pressure spec. being off spec.
Should be able to find the injector by doing as described in post #3 by gsholz
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11-29-2018, 10:20 PM
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#6
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Guru
City: Boston
Vessel Name: Adelante
Vessel Model: IG 30
Join Date: Nov 2016
Posts: 1,611
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You might be able to narrow down the source with a mechanics stethoscope. if knock is high on the engine you might have an injector problem or timing issue. If knock is low then it might be connecting rod wrist pin bearings that could fail due to high mileage, high load, blocked oil passage.
Might be a good idea to pay for an hour of diagnostic time from your local diesel expert. Knocks aren't good.
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11-29-2018, 10:31 PM
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#7
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Guru
City: Sydney
Vessel Name: Sojourn
Vessel Model: Integrity 386
Join Date: Oct 2011
Posts: 13,333
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Anyone know if Lehman 4cyl 80s engines have the same cooling passage silting issue as the 6cyl 120s do,at the last cylinder, gearbox end? Can you pinpoint the knock source?
__________________
BruceK
2005 Integrity 386 "Sojourn"
Sydney Australia
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11-30-2018, 05:21 AM
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#8
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Guru
City: Ft Pierce
Vessel Name: Sold
Vessel Model: Was an Albin/PSN 40
Join Date: Oct 2011
Posts: 28,149
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As far as the cooling issue...may want to call Brian at AD.
When I was redoing my damp er plate and asked about it....unless I was mistaken..... he said not to worry about it as it was more myth than reality.
Again, I could be mistaken but it might be an internet myth that keeps going.
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11-30-2018, 06:14 AM
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#9
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Technical Guru
City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
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Post a video (or audio) of the engine making the noise.
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11-30-2018, 06:41 AM
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#10
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Guru
Join Date: Oct 2007
Posts: 22,553
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Pulling the injectors is no big deal, and most shops will check them for free or $5.00 each , if they get to rebuild the bad ones.
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11-30-2018, 09:33 AM
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#11
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Guru
City: gulf coast
Join Date: Jun 2014
Posts: 3,440
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Use a stethoscope or even a length of hose to locate the source of the sound.
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11-30-2018, 10:33 AM
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#12
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Guru
City: East Coast
Vessel Name: M/V Maerin (Sold)
Vessel Model: Solo 4303
Join Date: Jun 2013
Posts: 886
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Unless you have a background in diesel engine service, your interpretation of a sound could be all over the spectrum. Even if you're somewhat of a gearhead, familiarity with the particular engine you're looking at goes a long way in qualifying a sound you're hearing.
Go ahead and learn as much as you can, but I'd still call in a pro. Let them have a look-see/listen without you offering up any conclusions or diagnosis. Then see if their observations have any parallel to your own. Don't get ahead of yourself.
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11-30-2018, 10:45 AM
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#13
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Guru
City: gulf coast
Join Date: Jun 2014
Posts: 3,440
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does the knock go away with increased rPM or in and out of gear?
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11-30-2018, 01:25 PM
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#14
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Guru
City: Brookline, NH
Vessel Name: Shalloway
Vessel Model: Defever 44, twin Perkins
Join Date: Sep 2013
Posts: 2,260
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One thing to keep in mind is that a failing damper plate can also cause a knocking that can sometimes sound like it's coming from the engine.
Ken
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12-07-2018, 01:49 PM
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#15
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Senior Member
City: Hawaii
Join Date: Jul 2018
Posts: 275
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Test as gsholz recommended then check for white smoke in the exhaust which my go away when the engine warms up, as may the knocking sound. If you have white smoke, stick your bare hand into the exhaust smoke then see if your hand feels oily. If so this is most likely is unburned fuel in the exhaust which is indicative of a bad injector. Dark smoke could mean lub oil in the exhaust, which probably won't go away when warmed up and could be much worse that a stuck injector.
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12-07-2018, 02:07 PM
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#16
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Member
City: Pensacola
Join Date: Nov 2018
Posts: 7
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Quote:
Originally Posted by ProMaritime
Test as gsholz recommended then check for white smoke in the exhaust which my go away when the engine warms up, as may the knocking sound. If you have white smoke, stick your bare hand into the exhaust smoke then see if your hand feels oily. If so this is most likely is unburned fuel in the exhaust which is indicative of a bad injector. Dark smoke could mean lub oil in the exhaust, which probably won't go away when warmed up and could be much worse that a stuck injector.
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It is white smoke and is clearly leaving a sheen of diesel on the water.
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12-07-2018, 02:08 PM
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#17
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Guru
City: Pender Harbour, BC
Vessel Name: Gwaii Haanas
Vessel Model: Custom Aluminum 52
Join Date: Sep 2013
Posts: 3,791
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Couple of issues - all diesels will put out "white smoke" this time of year. Every Fall there are posts about people freaking out over white smoke.
The only way to tell if it is the dreaded number 6 cylinder fail is to disconnect the injector and see if the sound gets lesser. It may, however, not silence the clunk if there is physical damage. A shortcut to determine if it IS number 6 is to remove the injector and use a camera to peer inside the cylinder. If it is number 6, you will see signs of cylinder scoring and a rebuild is necessary.
This is a reminder to all owners to read their manuals and "burp" the cooling jacket as per instructions. These engines were designed for horizontal installations in generators and combines etc and the fact that we tip them backwards when we stick them in a boat causes problems, as well as the proper oil level.
__________________
Don't believe everything that you think.
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12-07-2018, 06:17 PM
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#18
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Newbie
City: Brainbridge Island
Join Date: Mar 2015
Posts: 2
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While anchored in B.C. this past summer, I started my engine and an immmediate loud knocking sound emerged from the engine room. I limped into Canoe Cove Marina for a diagnosis by Raven Marine. What I thought was a bad injector turned out to be much worse. A camera scope in the #6 cylinder revealed scored lining and a damaged piston.
After removing the cylinder head, it was found that a valve seat dropped out which caused the valve to drop down and ride up and down on the piston, thus the loud knocking sound. The head was badly dimpled and damaged beyond repair.
Fortunately, my insurance company accepted my claim as an “accident” and covered the cost of my $36,000us repair bill, minus my deductible. My engine is a 14 year old Cummins 450c with 1673 hours that has been meticulously maintained and all service protocols have been followed since new by Cummins professionals.
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12-07-2018, 07:02 PM
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#19
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Enigma
City: Slicker?
Join Date: Oct 2007
Posts: 16,566
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Greetings,
Welcome aboard.
__________________
RTF
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12-07-2018, 08:03 PM
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#20
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Guru
City: Southport, FL near Panama City
Vessel Name: FROLIC
Vessel Model: Mainship 30 Pilot II since 2015. GB-42 1986-2015. Former Unlimited Tonnage Master
Join Date: Oct 2007
Posts: 4,984
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Another FL 120 horror story:
Loud clanking started on day while running down San Diego harbor. Heard clearly on the flying bridge. Turned out to be number six cylinder on port engine. Water had seeped down from one of those stupid over-the-engine muffler installations where the inner steel tube in the muffler can had rotted and into the cylinder where the damage was done before I bought the boat and before I had changed the exhaust to a down angle exit.
The engine had to be pulled, bored and all new pistons installed for $6,500 in 1987.
__________________
Rich Gano
FROLIC (2005 MainShip 30 Pilot II)
Panama City area
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