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Old 05-10-2009, 05:08   #1
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Vibration Under Floor from Driveshaft or ?

I have a Yanmar 4JH-TE engine with 650 hours.. It feels in the aft bedroom of a Hunter 42 I am getting a little vibration from the shaft. Not terrible just noticeable. Is this normal? Or what may be occurring and needed.
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Old 05-10-2009, 05:42   #2
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The danger is that, if you have a bent prop or shaft, the shaft may vibrate out of the key and wobble it's way out of the back of the boat. I have 2 S/S ring clips on my shaft to stop it backing all the way out of the boat.
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Old 05-10-2009, 06:00   #3
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Could be a few things
Growth on the prop
Worn Cutlass bearing
Prop shaft / transmission alignment off or coupling problems.
Bent or damaged shaft or prop
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Old 05-10-2009, 06:42   #4
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Probably a worn cutlass bearing .If possible dive on the boat and get your shoulder up underneath the shaft there should be almost no movement .If there is most probably have a worn cutless.

I have the same motor as you and have just had to realine my shaft {incorrect install} .I concluded that i had a mis alinghed shaft because my stuffing box was getting very hot.

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Old 05-10-2009, 08:02   #5
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vibration

I dove under the boat and the shaft is strong with no movement. Propeller has a few small barnacles but the hull is clean. Vibration is not strong but noticeable. Might this be normal???
Thanks for your response.
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Old 05-10-2009, 08:20   #6
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Barnacles could do it...did you scrape them off while you were down there....try it again?
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Old 05-10-2009, 20:19   #7
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- - Are you anchored out or in a marina hooked up to shore power? If in a marina for a long time with leaking shore power - the most down facing propeller blade will start to dissolve (electrolysis) and eventually unbalance the propeller.
- - If anchored out then look elsewhere like the suggested barnacles or dent or bent tip in the prop. You eliminated cutlass bearing wear so maybe try jury-rigging a pencil inside the prop shaft area so that the tip almost touches the prop shaft. Then rotate the shaft to see if there is something out of line which will result in the pencil tip touching the shaft. Also worn rear engine mounts can allow the prop shaft to vibrate as the engine moves when running. With the engine running see if the pencil touches the shaft.
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Old 05-10-2009, 20:49   #8
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Thanks I am in Marina, I saw some small small barnacles on the prop when i dove.. prop is auto prop new in 2005. I just bought the boat and did no sea trial because price was very good....

Question Is a little vibration normal, it would seem It doesn't knock you down or anything. Just standing in rear bedroom a slight vibration. I think bearings were checked and repacked less than 100 hours on engine before.
Engine does not seem to shake at all when running. It vibrates the floor board in aft bedroom but would not upset a wine glass setting on the floor or move it.

Vibration occurs at 1500 and 2000 and 2500 rpms. Does not vary as rpm's increase.
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Old 05-10-2009, 21:15   #9
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Are you sure its not normal? Does it vibrate out of gear?
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Old 05-10-2009, 22:18   #10
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No vibration out of gear.... No sure what normal feels like

Yanmar 65 hp
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Old 06-10-2009, 00:49   #11
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Resonance...

If you're only getting the vibration at particular engine speeds it's most likely at least partly due to the boat (or part thereof) resonating in tune with the engine.

Think of it as being like a tuba playing a note.

Simple solution:- If this is the case don't run at those engine speeds.
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Old 06-10-2009, 06:50   #12
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Vibration

It vibrates at all engine speeds. On a 1-10 scale it vibrates 2-3

Cutlass bearing was replaced on 11/04.

Work order says. Pull prop shaft coupling and stuffing box. Replace cutlass bearing install PYI dripless shaft seal and plumb. Clean and service prop.

1 Chogset Cutlass Bearing $73.87
1 1 1 /4 x 2 1/4 Shaft seal PYI $260.00


Engine hours since replacement is less than 100. Boat has been in the water since then.

Bottom cleaned once a month
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Old 06-10-2009, 07:14   #13
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>>> prop is auto prop new in 2005. I just bought the boat and did no sea trial because price was very good....<<<<
- - Aha! that does make a big difference. I used to sell and service the AutoProp. Dive under the boat if it is in the water - and - with some sort of bracing, try to shove the AutoProp further up onto the prop shaft and also try to pull it off the prop shaft. If there is any degree of movement forward (up onto the prop shaft or away/off the prop shaft) do not operate the vessel!
- - Assuming the boat is in the water, Tie a secure rope around the AutoProp and to an anchor point on the top of the boat - you are going to partially remove the AutoProp from the shaft so you need to make sure it does not drop into the mud/sea-bottom under the boat. AutoProps are very, very heavy. Remove the cover from the end of the hub and examine the tube-nut. If there is a cotter pin through the nut part of the tube-nut remove it to see if it is sheared.
- - If there is no cotter pin through the tube-nut use a very large long handled wrench and try to tighten the tube-nut. If you can tighten it - then you will need to haul the boat out of the water to make a modification to the AutoProp. PM me and I will explain what you need to do.
- - If the AutoProp is tightly secured to the prop shaft and no movement is possible and the tube-nut cannot be further tightened - then most likely your cutlass bearing or other bearing through which the prop shaft passes as it exits the hull is badly worn.
Some boats use a sealed pillow block bearing instead of a cutlass bearing. With great strength check to see in you can move the whole AutoProp and shaft up and down or left and right. You are checking for a worn cutlass bearing. If you find a worn cutlass bearing then the boat will need to be hauled. PM me and I will tell you of the proper type cutlass bearing to use with the AutoProp.
- - The AutoProp is extremely heavy compared to normal fixed blade props or even other folding/feathering props. This wears out the cutlass bearing very quickly and at certain rpm's the harmonics will cause the prop and shaft to vibrate.
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