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Old 21-07-2010, 02:59   #1
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Excess Engine Vibration

Excess engine vibration , 4 year old boat 1200 hours/ 3ym30 with sail drive-I have one engine that has a vibration , seems to run well, it overheated once when a belt broke but was turned off right away, and it does not seem to affected by that- Iíve looked at the motor mounts and they look fine, nothing obviously wrong,- the air intake filter was a little more dirty with black soot than the other engine, and I have had some bad fuel , but Iím watching the filters closely keeping them changed- Iím kind of thinking itís an injector not working at 100% any ideas? How can I tell if itís a motor mount? Can running it if itís an injector problem case damage,?
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Old 21-07-2010, 05:56   #2
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Can running it if itís an injector problem case damage,?
Eventually, yes, it can. If it is an injector and it completely stops working, the piston will "flop around" in the cylinder, the best way I can describe it, because it isn't producing any power. It can ruin your cylinder sleeve and/or piston. If it sticks open, that's when you get tons of smoke from unburnt fuel making it into the exhaust.

An injector that is going bad will sometimes puff dark gray smoke out the exhaust before it fails completely.

Have you tried any injector cleaners or other fuel additives?

Have the valves been adjusted since it was new? That might be something to look at. I have this done on my road tractors on a regular schedule and will when I buy a boat with an inboard diesel. When those valves tighten down too much they don't close all the way and produce the symptoms you describe.
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Old 21-07-2010, 08:12   #3
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Eventually, yes, it can. If it is an injector and it completely stops working, the piston will "flop around" in the cylinder, the best way I can describe it, because it isn't producing any power. It can ruin your cylinder sleeve and/or piston. If it sticks open, that's when you get tons of smoke from unburnt fuel making it into the exhaust.

An injector that is going bad will sometimes puff dark gray smoke out the exhaust before it fails completely.

Have you tried any injector cleaners or other fuel additives?

Have the valves been adjusted since it was new? That might be something to look at. I have this done on my road tractors on a regular schedule and will when I buy a boat with an inboard diesel. When those valves tighten down too much they don't close all the way and produce the symptoms you describe.
No it has not had any kind of off smoke at all come out, but the valves , i know its past time on there ajustment, so thats what im gonna try next, thanks for that tip I will let you know if it works, -I cant get to it for a few weeks
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Old 21-07-2010, 09:55   #4
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How can I tell if itís a motor mount?
You can't always tell about motor mounts just by looking at them. Try wedging something soft (like a wooden dowel, not like a screwdriver) under them to see if the engine settles down. Vibration problems tend to break mounts, so once one goes it sometimes has a domino effect on the others.
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Old 21-07-2010, 16:27   #5
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First.....check the motor mount located directly under the secondary fuel filter.....

Diesel fuel kills those mounts.
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Old 22-07-2010, 04:31   #6
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1000hrs is the recommended interval to pop test and spray pattern test the injectors.
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Old 22-07-2010, 05:24   #7
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Why not try coming at it from another direction.
1 You have had bad fuel and the injectors have not been serviced for a long time so pull them and have them serviced
2 Adjust the tappets as they are due to be done

Once all these overdue service items have been attended to see if the vibration is gone. Even if the vibration is still evident your engine is going to be running cleaner and engine life extended and you can concentrate on other areas like engine mounts. On the other hand you may find it is fixed and the engine has been serviced as well. Change the engine oil + filter while your at it.
My thinking is why go looking at items that appear to be okay while ignoring others that you now need attention and could be causing the vibration?
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Old 22-07-2010, 22:04   #8
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Thanks Guys, What is the Valve adjustment setting on a 3ym30 Yanmar??
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Old 23-07-2010, 14:46   #9
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Ram, There is a simple way to test your injectors. While engine is running above idle... try about 1800 RPM... open the fuel line nut going into each injector one-at-a-time. As you open each one, note the RPM drop for each cylinder. If one or more cylinder has minimal RPM drop, that will indicate an injector or compression problem on that cylinder.

When I did this test on my 3 cylinder Volvo, the RPM drop on #1 and #3 was over 200. On the cylinder with a bad valve the RPM drop was less than 100 RPM.

Note: wrap a rag around top of injector when doing this since a little fuel will squirt out around the nut.
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Old 24-07-2010, 08:56   #10
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you are due for a propshaft alignment at 1000 hrs. if you have an engine vibration issue at 1200 hours i'd first suspect that your engine mounts are due for an adjustment. age and wear compresses these flexible mounts. yanmar recommends replacement at 1000 hrs or 4 years although i've gotten 10 yrs out of mounts when the boat is only run 6 months of the year and store on the hard for the other 6. check the faceout with a feeler gauge at 4 places where your prop shaft couples to your driveshaft. excess clearances at the upper end of this coupling as compared to lower end ie measurements between the prop end and the crank end taken at 12 oclock 2 oclock and 10 o clock being bigger and wider apart than the clearances at 8 oclock 6 oclock or 4 oclock suggests you need to adjust UP and higher the engine mounts both front and rear. sorry i cant be more specific on what the distances should be as i don't have the install manual for that engine..but generally speaking the faceout should be the same off maybe .0001 when measured around the coupling. (yanmar doesn't give you the f faceouts any more in the 'SERVICE manual, you have to look at the "INSTALL manuals..instead of a particular install manual for each engine they now have a MASTER INSTALL manual that has a a bunch of pages for each engine...
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Old 24-07-2010, 09:07   #11
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...the faceout should be the same off maybe .0001
Nothing on a engine is built to .0001 inch. Surely you meant .001 inch/inch runout for a propshaft flange.
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Old 24-07-2010, 12:36   #12
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I ajusted the valves today and that helped some its about 1/3 less vibration now, and I did not mention this is mostly at low idle, below 900 rpms -still not perfect-Good advice Greg and Mitch I have a sail drive so I dont think thats an issue- the motor mounts seem ok as it only vibrates at low rpm-
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Old 24-07-2010, 13:00   #13
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I find my saildrives are very sensitive to ANY fouling of the props. At least where I am I have to dive them at least once a week. A few small barnacles and a slight off balanced prop will be amplified on the sail leg transfering the shake to the engines.
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