Greetings friends, My 1977 H-33 with an original QM20, has always had a nasty vibration that gets worse with the level of power. I'm afraid to run the thing at full throttle for fear of breaking something! The folks at Torenson told me all the QM series Yanmars were known for vibration. Being an auto mechanic with some experience with diesels, I would like to correct this condition or at least minamize it. I have already relaced the strut bearing, prop, and shaft. I also checked the flange alignment. Next I think I'd like to check the motor mounts. Can anyone tell me the best way to check them? If it was a car I would power break it in forward and then reverse and look for the engine to lift. I'm wondering if anyone reading this has experience with replacing the mounts on an old QM engine? Must I buy the expensive Yanmar mounts? Do you folks think this will help my vibration issue? Thanks, Don Bodemann
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D
David
QM
Don I have the same engine and have done all the things you mentioned plus pulled a mount. The mount was almost as good as new. Still shakes but keeps on going. This series engine was the strongest Yanmar has made.
Don I have the same engine and have done all the things you mentioned plus pulled a mount. The mount was almost as good as new. Still shakes but keeps on going. This series engine was the strongest Yanmar has made.
C
Colin
Check your prop also.
You could also check your prop! Have an engineering friend in the marina who ballanced his prop on a home made rig and found it made a big difference to the vibration while under power. Not sugesting you do this unless you feel confident with it, but you could take it to a prop shop and have them check it.
You could also check your prop! Have an engineering friend in the marina who ballanced his prop on a home made rig and found it made a big difference to the vibration while under power. Not sugesting you do this unless you feel confident with it, but you could take it to a prop shop and have them check it.
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Don
Model plane props Colin
Actually Colin, I have a prop balancer for my large scale model planes that would probably do the trick. On the other hand, the prop I'm now using is brand new and didn't make a diferrence over the old prop.
Actually Colin, I have a prop balancer for my large scale model planes that would probably do the trick. On the other hand, the prop I'm now using is brand new and didn't make a diferrence over the old prop.
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Don
Mounts David?
Dave, Nice to hear my engine has a good reputation. I'm wondering if the mounts from Yanmar are somewhat generic to Yanmar (they use the same type of mount for all their engines)? Perhaps a harder mount or a softer mount would improve the situation? Any thoughts?
Dave, Nice to hear my engine has a good reputation. I'm wondering if the mounts from Yanmar are somewhat generic to Yanmar (they use the same type of mount for all their engines)? Perhaps a harder mount or a softer mount would improve the situation? Any thoughts?
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MArk
Mover and shaker?
Hi Don, Try to isolate the problem. Your vibration is either from the engine or the propeller shaft. Does the engine still cause the vibration when the shaft coupling is disconnected? If not, is your propeller shaft straight? Does your coupling have rubber bushings? If so, are they worn? Is the coupling properly aligned? Is a lack of lubrication in the shaft packing causing the vibration? Bad bearings? I’m not really familiar with your particular boat/engine but just thought I'd offer a few suggestions. See related link too. Happy sails _/), MArk
Hi Don, Try to isolate the problem. Your vibration is either from the engine or the propeller shaft. Does the engine still cause the vibration when the shaft coupling is disconnected? If not, is your propeller shaft straight? Does your coupling have rubber bushings? If so, are they worn? Is the coupling properly aligned? Is a lack of lubrication in the shaft packing causing the vibration? Bad bearings? I’m not really familiar with your particular boat/engine but just thought I'd offer a few suggestions. See related link too. Happy sails _/), MArk
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MArk
Missing link?
Hi again Don, After changing the motor mounts and pulling and inspecting the tranmission ($600 total) and not seeing any improvement, a simple shift-lever adjustment did the trick. See the related link. Worth a try! Happy sails _/), MArk
Hi again Don, After changing the motor mounts and pulling and inspecting the tranmission ($600 total) and not seeing any improvement, a simple shift-lever adjustment did the trick. See the related link. Worth a try! Happy sails _/), MArk
K
Kevin
Better garde of mounts?
Hello Don, Since the Yanmar mounts are compression style mounts changing out to preloaded mounts maybe an option. Your Yanmar mounts require the weight of the engine to compress the rubber in the mounts. This compression may have a dimension of ¼” in all directions. A preloaded mount may have a deflection rate of .09. This difference may help to keep the engine from moving so far. Once the inertia of the motor starts it becomes very difficult to slow it down unless the mounts offer resistance from the get go. If you have any other questions please let me know. kwoody@pyiinc.com Hope this helps Kevin.
Hello Don, Since the Yanmar mounts are compression style mounts changing out to preloaded mounts maybe an option. Your Yanmar mounts require the weight of the engine to compress the rubber in the mounts. This compression may have a dimension of ¼” in all directions. A preloaded mount may have a deflection rate of .09. This difference may help to keep the engine from moving so far. Once the inertia of the motor starts it becomes very difficult to slow it down unless the mounts offer resistance from the get go. If you have any other questions please let me know. kwoody@pyiinc.com Hope this helps Kevin.
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