I have a Yanmar 3gm30f 1984 with 475 hrs. It has a vibration that's driving me nuts! This is an engine vibration that only manifest itself at certain rpms. Smooth as silk to about 1200 in or out of gear. Vibration increases with rpms to about 1800 where it smooths out. (or reaches resonance) The motor itself is not vibrating/shaking much, but everything else on the boat is! First, I thought it was a drivetrain issue, but since it still did it in nuetral... Anyway, I removerd the transmission, as I had blown a rear tranny seal a while back and thought maybe I had warped a plate. Vibration, if anything was worse. (with the tranny removed) I had the injectors checked. One bad so it was rebuilt. Ah ha I thought....No luck. Engine runs better thus making the vibration more noticeable! Engine mounts. With motor running and vibrating I pried up on the mounts to see if maybe I had a bad mount. Prying up on the port rear seemed to help so I pulled it. Was in perfect shape. I called to see how much a compression check would be, $140.00!!! I have the tools to do this for an auto but not diesel. What do I need and where to buy a compression set for diesel? Should this be my next step? I'm thinking maybe a valve issue??? ANY HELP WOULD BE APPRECIATED! Thanks Tom 'Hearts Desire'
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Not that uncommon.
Tom: It is not that uncommon to have these vibrations. Is your engine smooth enough at 2500-3000 rpms?
Tom: It is not that uncommon to have these vibrations. Is your engine smooth enough at 2500-3000 rpms?
Yes but...
Thanks for your response, but this vibration is not normal engine vibration and should not be there. This is serious vibration at these rpms. At it's most intense, you cannot sit in the cockpit as the seats are vibrating enough to be uncomfortable. The vibration is manifested throughout the boat as opposed to actual engine shake. (hard to explain)I've worked on auto engines enough over the years, and just know that this is abnormal and should be fixed. Tom
Thanks for your response, but this vibration is not normal engine vibration and should not be there. This is serious vibration at these rpms. At it's most intense, you cannot sit in the cockpit as the seats are vibrating enough to be uncomfortable. The vibration is manifested throughout the boat as opposed to actual engine shake. (hard to explain)I've worked on auto engines enough over the years, and just know that this is abnormal and should be fixed. Tom
Tom, be sure to run this one past Yanmarhelp.com
They should help you solve it. All I can think to do, that you haven't mentioned is, while the engine is vibrating, try releasing each of the compression releases. If one of the cylinders causes the engine to run less poorly than the other(s), it's not doing it's share. Just like pulling a spark plug wire from a distributor cap. Good luck and be sure to keep us posted. And those low hours might have something to do with it. Injector pump maybe? No water in the oil?
They should help you solve it. All I can think to do, that you haven't mentioned is, while the engine is vibrating, try releasing each of the compression releases. If one of the cylinders causes the engine to run less poorly than the other(s), it's not doing it's share. Just like pulling a spark plug wire from a distributor cap. Good luck and be sure to keep us posted. And those low hours might have something to do with it. Injector pump maybe? No water in the oil?
injector pump?
Thanks Fred. Did not know about Yanmarhelp. While engine was running poorly I cracked each fuel line at the injector to see what change this would have. The resulting engine performance was identical for all three cylinders. (did i mention this is driving me NUTS!
Is there a way to check the injector pump? Does it have to be removed? Is this a symptom of injector pump trouble? Tom
Thanks Fred. Did not know about Yanmarhelp. While engine was running poorly I cracked each fuel line at the injector to see what change this would have. The resulting engine performance was identical for all three cylinders. (did i mention this is driving me NUTS!
Is there a way to check the injector pump? Does it have to be removed? Is this a symptom of injector pump trouble? Tom
Tom, on the injector pump,
I have to defer to yanmarhelp.com. Seems as though there is a flow test to measure the fuel delivery volume, but other than that??? Here's what my manual says, under trouble shooting: Trouble: Output of the cylinders uneven; 1. air in fuel pump or line. 2. water in fuel. 3. fuel injector volume uneven. 4. fuel injector timing uneven. 5. intake and exhaust valves sticking. 6. injection valve faulty. Corrective action: 1. prime and bleed. (of course) 2. drain the fuel tank and system. (again, of course) 3. check and adjust injection volume. (there is a chapter in the manual telling what to do) 4. check and adjust injection timing. (I've done this. Shims are needed under the pump. Also a orifice in place of an injector. Simple tool, but not an end user toolbox item. And the timing is almost never off.) 5. disassemble and clean. 6. if nozzle is clogged, clean; replace nozzle if necessary. If needle is sticking, inspect and replace. This stuff is in the back of my shop manual, a good book to have and not all that much cash. P.S. You know to check the exhaust elbow first right? P.S.2 Your test of cracking the fuel lines sounds like your pump in fine. (just guessing) But remember, it doesn't tell you what is happening in the cylinders. Be sure to check for even work load with the releases. You checked the elbow right?
I have to defer to yanmarhelp.com. Seems as though there is a flow test to measure the fuel delivery volume, but other than that??? Here's what my manual says, under trouble shooting: Trouble: Output of the cylinders uneven; 1. air in fuel pump or line. 2. water in fuel. 3. fuel injector volume uneven. 4. fuel injector timing uneven. 5. intake and exhaust valves sticking. 6. injection valve faulty. Corrective action: 1. prime and bleed. (of course) 2. drain the fuel tank and system. (again, of course) 3. check and adjust injection volume. (there is a chapter in the manual telling what to do) 4. check and adjust injection timing. (I've done this. Shims are needed under the pump. Also a orifice in place of an injector. Simple tool, but not an end user toolbox item. And the timing is almost never off.) 5. disassemble and clean. 6. if nozzle is clogged, clean; replace nozzle if necessary. If needle is sticking, inspect and replace. This stuff is in the back of my shop manual, a good book to have and not all that much cash. P.S. You know to check the exhaust elbow first right? P.S.2 Your test of cracking the fuel lines sounds like your pump in fine. (just guessing) But remember, it doesn't tell you what is happening in the cylinders. Be sure to check for even work load with the releases. You checked the elbow right?
exhaust elbow and misc
Exhuast elbow is new (within a yr) Injectors just done at a diesel shop. One nozzle replaced. Fuel tank is brand new as is the fuel and a new racor w/the h20 serarator. As I recall, this problem started out at about 800 rpm. First noticed it when coming into the slip one day. 800 is now fine as the problem has moved up the rpm scale. Will these things even run with air in the line? Your efforts are appreciated. Tom
Exhuast elbow is new (within a yr) Injectors just done at a diesel shop. One nozzle replaced. Fuel tank is brand new as is the fuel and a new racor w/the h20 serarator. As I recall, this problem started out at about 800 rpm. First noticed it when coming into the slip one day. 800 is now fine as the problem has moved up the rpm scale. Will these things even run with air in the line? Your efforts are appreciated. Tom
Yes! They run well too, with air in the line.
Bleeding is like horseshoes and hand grenades. Honest. This is sounding more and more like a internal valve/piston problem. Easy to fix.
Bleeding is like horseshoes and hand grenades. Honest. This is sounding more and more like a internal valve/piston problem. Easy to fix.
Easy?!!
Want to come to Florida? What should my next efforts be? After bleeding again. I assume a compression check is in order? Where to get a good deal on the tester? Is this something I can do? It's no big deal on a car. Thanks Tom
Want to come to Florida?
What should my next efforts be? After bleeding again. I assume a compression check is in order? Where to get a good deal on the tester? Is this something I can do? It's no big deal on a car. Thanks Tom
Tom I defer to Fred but
with the boat shaking more than the engine and since you are going nuts anyway, why not check the engine bed or whatever you call the structure the mounts are anchored to, since it sounds like the engine has grabbed a big piece (but not all) of the boat and is shaking it.
with the boat shaking more than the engine and since you are going nuts anyway, why not check the engine bed or whatever you call the structure the mounts are anchored to, since it sounds like the engine has grabbed a big piece (but not all) of the boat and is shaking it.
Maybe it's not the engine after all..
Tom: I know you checked the tranny, but maybe one of the "normal" vibration causes may be at work here if the engine is running smoohly.... - drive shaft - shaft alignment - prop (damage, marine growth) - shaft hitting the hull in the tube - loose motor mounts (even slightly)both to the hull and to the rubber (lots of personal experience here) Even if the alignment looks good, double check. I just did mine, and even though within tolerences, I adjusted slightly and it feels like I have a new boat and engine... real smooth now. Good luck.... Jeff
Tom: I know you checked the tranny, but maybe one of the "normal" vibration causes may be at work here if the engine is running smoohly.... - drive shaft - shaft alignment - prop (damage, marine growth) - shaft hitting the hull in the tube - loose motor mounts (even slightly)both to the hull and to the rubber (lots of personal experience here) Even if the alignment looks good, double check. I just did mine, and even though within tolerences, I adjusted slightly and it feels like I have a new boat and engine... real smooth now. Good luck.... Jeff
Tom, the mount
you said you pulled up on and it seemed to help. Maybe you just forced the engine onto the bad mount. The bad one could be opposite of the one you checked. And I do wish I were there. Seriously. I'm one of those guys who 'feels' what the engine is doing just standing next to it. Be sure to do the compression release test. It's cheap but not as accurate as a real tester. But it could tell you if you need the tester right away. P.S. The compression tester for a diesel is not cheap. I heard of one on ebay last month for about $160. You could get a mechanic to come to the boat and do the test for about half that money. (or less)
you said you pulled up on and it seemed to help. Maybe you just forced the engine onto the bad mount. The bad one could be opposite of the one you checked. And I do wish I were there. Seriously. I'm one of those guys who 'feels' what the engine is doing just standing next to it. Be sure to do the compression release test. It's cheap but not as accurate as a real tester. But it could tell you if you need the tester right away. P.S. The compression tester for a diesel is not cheap. I heard of one on ebay last month for about $160. You could get a mechanic to come to the boat and do the test for about half that money. (or less)
Thanks Jeff
Thanks, but the tranny is still out so no drive train is involved. Believe me, these were the first things I tried. ps. I used to race 30' Tartan class out of the Edgewater Yacht Club many years agao! Tom
Thanks, but the tranny is still out so no drive train is involved. Believe me, these were the first things I tried. ps. I used to race 30' Tartan class out of the Edgewater Yacht Club many years agao! Tom
Fred...
Fred, please explain the compression release test. Local mechanics want 140. to come out and check the compression. I'm one of those people who hate to pay someone to do something I can do. Although, I don't mind paying if it is beyond my capabilities. Thanks Tom
Fred, please explain the compression release test. Local mechanics want 140. to come out and check the compression. I'm one of those people who hate to pay someone to do something I can do. Although, I don't mind paying if it is beyond my capabilities. Thanks Tom
Tom, did you notice the reference I made to
the removal of the spark plug wires at the distributor of a gas engine? When you are looking for a bad running cylinder, note the engine speed on the tach and take each cylinder off line one at a time. The one(s) that fails to drop engine speed is not working. This test on a 3 cylinder diesel is sure not that precise. I wouldn't even mess with the tach. If one is not working as well as the others, it should be apparent. Take the engine up to vibration speed and open one release at a time. The bad cylinder will show less change.
the removal of the spark plug wires at the distributor of a gas engine? When you are looking for a bad running cylinder, note the engine speed on the tach and take each cylinder off line one at a time. The one(s) that fails to drop engine speed is not working. This test on a 3 cylinder diesel is sure not that precise. I wouldn't even mess with the tach. If one is not working as well as the others, it should be apparent. Take the engine up to vibration speed and open one release at a time. The bad cylinder will show less change.
Fred...
Yes, I understand the principle. Wish this was as simple as replacing a faulty wire. I am probably missing something simple. I will go back to the basics to make sure that I have not. Thank you. Your suggestions and speedy replies are most appreciated. I will keep my progress posted. Tom
Yes, I understand the principle. Wish this was as simple as replacing a faulty wire.
I am probably missing something simple. I will go back to the basics to make sure that I have not. Thank you. Your suggestions and speedy replies are most appreciated. I will keep my progress posted. Tom
Good luck Tom
Keep in mind that there isn't much that can cause this problem. In other words, don't try to make it a deep black mystery. OK, 'keep it simple stupid'.
Keep in mind that there isn't much that can cause this problem. In other words, don't try to make it a deep black mystery. OK, 'keep it simple stupid'.
A try
Not sure I want to get in this wide open discussion, but my experience might help. When I first started using a 1980 Yanmar two years ago, it had similar rough spots at varying rpm. I was then using commerial marina diesel. By changing to the best Hiway diesel I can find. Pre-filtering it with a water-filter funnel, adding a power booster, and bio-bor the engine now starts easily and runs soothly. I believe the cetane booster is the most important element along with fresh clean fuel.
Not sure I want to get in this wide open discussion, but my experience might help. When I first started using a 1980 Yanmar two years ago, it had similar rough spots at varying rpm. I was then using commerial marina diesel. By changing to the best Hiway diesel I can find. Pre-filtering it with a water-filter funnel, adding a power booster, and bio-bor the engine now starts easily and runs soothly. I believe the cetane booster is the most important element along with fresh clean fuel.
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