Engine shaking

[tothecut]

Hi everyone, a few weeks ago I noticed the engine started to shake sometimes, when putting it into a forward gear. It only happens in forward and disappears after adding revs. It's really bad, the engine, the gearbox and the shaft shake a lot and I am very worried.

Any help appreciated.

[b00ke23]

Loose/broken/worn engine mounts? What sort of engine is it?

[tothecut]

3 minutes ago, b00ke23 said:

Loose/broken/worn engine mounts? What sort of engine is it?

The engine is a Vetus M4.17

The engine mounts seem to be fine, although I am not an expert.

One thing which happened before it started was that time when I turned the engine off while in gear (gearbox cable broke) and I was in panic. Is it possible that it's a problem with the gearbox?

[Tony Brooks]

4 minutes ago, tothecut said:

The engine is a Vetus M4.17

The engine mounts seem to be fine, although I am not an expert.

 

Would it have a Vetus packless stern gland and a Cutless rubber shaft bearing. If so, is anything around the prop or is the prop bent. Under the right circumstance and with that bearing/gland combination, I feel an out of balance prop could wave the engine about via the shaft. I would have expected it to be at higher revs, not idle.

 

I think most Vetus mounts are "suspend the engine part way up a stud between two nuts" type and if so the bottom nuts do come loose and if you are not aware unbalance the mounting forces. So get a suitable spanner and try tightening the nuts BELOW the engine foot up against the engine foot. Do NOT tighten the top nut down. They are usually (but not always) self-locking and rarely move.

 

Perhaps more likely the engine has developed a low speed misfire, only running on three cylinders, so post a video of it if you can so we can hear what it sounds like. Check no valve clearances have closed up - or are exceptionally large.

[magnetman]

An article of clothing around the propeller could do this. 

 

First thing to check. 

Oops did not read it properly. It goes away as speed is added. Probably not the prop foul then although still worth eliminating. 

 

[system 4-50]

42 minutes ago, tothecut said:

(gearbox cable broke)

is there any extra info about this event?  Did it require unusual force? Was there any unusual gearbox behaviour at the time?

[Tony Brooks]

44 minutes ago, tothecut said:

One thing which happened before it started was that time when I turned the engine off while in gear (gearbox cable broke) and I was in panic. Is it possible that it's a problem with the gearbox?

 

 

 

I would say extremely unlikely from just doing that. Anything is possible, it is possible that the gearbox drive plate is breaking pp with the boss running or trying to run off-centre, but very unlikely to be caused by turning it off while in gear.

[tothecut]

3 minutes ago, system 4-50 said:

is there any extra info about this event?  Did it require unusual force? Was there any unusual gearbox behaviour at the time?

As we were going to moor up for the night, I wanted to put the gearbox in neutral, but it didn't respond. I panicked and turned the engine off while still in forward gear. Apart of that, nothing out of ordinary happened.

[MtB]

14 minutes ago, tothecut said:

As we were going to moor up for the night, I wanted to put the gearbox in neutral, but it didn't respond. I panicked and turned the engine off while still in forward gear. Apart of that, nothing out of ordinary happened.

 

I wouldn't call that panicking. I'd call that a sensible and correct decision based on what was happening. 

 

 

[tothecut]

I checked the prop and the shaft, everything seems to be fine. I tried to tighten the nuts, but they're tight already. Can't check the valve clearances right now, as the engine needs to cool down. I recorded when it's all right and when it's shaking.

https://veed.io/view/5d46744d-9e20-4298-a870-da4d8935ca4b

https://veed.io/view/e7d9d7fa-af9d-4949-ac30-f7500dde6ff0

 

 

[Tony Brooks]

12 minutes ago, tothecut said:

I checked the prop and the shaft, everything seems to be fine. I tried to tighten the nuts, but they're tight already. Can't check the valve clearances right now, as the engine needs to cool down. I recorded when it's all right and when it's shaking.

https://veed.io/view/5d46744d-9e20-4298-a870-da4d8935ca4b

https://veed.io/view/e7d9d7fa-af9d-4949-ac30-f7500dde6ff0

 

 

 

That is weird, the shake is so sedately with no apparent relationship to engine speed. All I can think of is diagonally out of alignment engine mounts, but that does not suddenly happen. It sounds clattery, but that is probably just the frequency response of the phone microphone, but I could not detect a misfire from the sound. Anyway, the movement was too slow for that, I feel.

 

Try to get a lever between the engine bed and the metal cap shroud on the mounts. Lever the shroud and thus the engine up, each mount in turn and judge if any move further for the same effort or move just as much as the rest but with a bit less effort. That may give you an idea if any of the mount rubbers have collapsed.

 

I await other ideas with great interest.

[MtB]

1 minute ago, Tony Brooks said:

That is weird, the shake is so sedately with no apparent relationship to engine speed.

 

Looks weird to me too, the engine block seems to be distorting slowly back and forth on my screen, which clearly cannot be happening. 

 

I think there must be some sort of interference or Doppler effect between the frame rate of the recording and the engine oscillating really fast. Or possibly the replay frame rate on our PCs.

 

 

 

[tothecut]

11 minutes ago, Tony Brooks said:

That is weird, the shake is so sedately with no apparent relationship to engine speed

This must be something with the recording, because there's no that slow sideways movement when just looking at the engine working. Anyways, I'm going to try and check the mounts right now.

[nicknorman]

Yes I think the video frame rate is creating a false impression. Could you take the video again and vary the engine rpm?

 

That said I think it is likely to be a fractured engine mount or engine foot. When the engine is stopped, maybe it is just resting on the fracture? I would wait for it to cool and apply some rocking force with a foot etc whilst checking each mount area closely, to see if there is movement where there shouldn't be.

[b00ke23]

There's a bit of rolling shutter effect on that video making it look weird. If you can, experiment with differemt frame rates and film it again, hopefully it'll look normal. 

[tothecut]

28 minutes ago, nicknorman said:

Yes I think the video frame rate is creating a false impression. Could you take the video again and vary the engine rpm?

Won't be able to do that, it only happens in tickover, when I add revs, it stops.

Most likely it's the problem with the engine mounts, but this isn't something I would be confident fixing myself. Does anyone know of a good engineer around Burton on Trent?

Thanks everyone for your advice.

[Tony Brooks]

8 minutes ago, tothecut said:

Does anyone know of a good engineer around Burton on Trent?

 

Not used their engineering, side but Jannel Cruisers were very helpful with making up alternator leads for me on a Bank Holiday Saturday.

[blackrose]

12 minutes ago, tothecut said:

Won't be able to do that, it only happens in tickover, when I add revs, it stops.

 

 

My Isuzu engine tends to be a bit lumpier when idling than when revved, especially when starting from cold. That really gives the mounts a workout, so I usually try to set the revs to around 1000 rpm before starting the engine. 

 

Are you sure your idling speed hasn't dropped for some reason? I think you mentioned a control cable snapping earlier in the thread.

[magnetman]

It was the gearbox cable. 

 

Not every day that one of these fails.

 

One wonders why it failed and the box jammed in ahead gear. 

 

This has since evidently been fixed but why did it happen? 

 

 

 

 

3 hours ago, tothecut said:

 

One thing which happened before it started was that time when I turned the engine off while in gear (gearbox cable broke) and I was in panic. Is it possible that it's a problem with the gearbox?

 

 

 

i wonder if a prop jammed by a piece of wood might cause the gearbox to not operate. If it is a hydraulic gearbox it won't do anything when not turning. 

 

Does the M417 have a hydraulic box? 

 

I am wondering if you have a slightly bent shaft or prop but that would presumably present problems at all speeds not just at tickover. 

 

 

Wrong tickover setting is certainly an interesting suggestio

 

 

Did the morse cable fail at the control box or at the gearbox end? 

 

 

[tothecut]

8 minutes ago, magnetman said:

Did the morse cable fail at the control box or at the gearbox end? 

Gearbox end

 

9 minutes ago, magnetman said:

the box jammed in ahead gear. 

It didn't. It was in gear when the cable broke. I could reach and get it in neutral manually, but as I said, I panicked.

 

26 minutes ago, blackrose said:

Are you sure your idling speed hasn't dropped for some reason? I think you mentioned a control cable snapping earlier in the thread.

It's possible. But I tinkered with the cable a bit and it didn't help. It's a Technodrive gearbox 2:1 and was pretty obvious how the cable should be replaced.

[Tony Brooks]

23 minutes ago, magnetman said:

One wonders why it failed and the box jammed in ahead gear. 

 

This has since evidently been fixed but why did it happen? 

 

 

Normally simple old age or re-routing cables through tight radiuses.

 

I don't think the OP meant the box actually jammed. more likely, the broken cable prevented him getting it out of gear on the control.

[magnetman]

The gearbox cable is nothing to do with engine idle speed. Two separate cables. 

 

I was wondering if the gearbox had momentarily jammed in ahead gear breaking the cable when you tried to shift to neutral. By the time you got to it the prop foul may have dislodged itself. 

 

 

Just speculation most probably wrong but a shaking engine can be related to bent prop or shaft which had been caused by an instantaneous prop foul like a piece of 2x4 being in the right place at the right time. 

 

 

Edited August 12 by magnetman

[Tony Brooks]

2 minutes ago, tothecut said:

Gearbox end

 

It didn't. It was in gear when the cable broke. I could reach and get it in neutral manually, but as I said, I panicked.

 

It's possible. But I tinkered with the cable a bit and it didn't help. It's a Technodrive gearbox 2:1 and was pretty obvious how the cable should be replaced.

 

There is no difficulty replacing/adjusting gear cables, it is the throttle cables that tend to have a gotya when replacing. A broken gear cable should not have any effect on the throttle cable adjustment.

[tothecut]

1 minute ago, Tony Brooks said:

There is no difficulty replacing/adjusting gear cables, it is the throttle cables that tend to have a gotya when replacing. A broken gear cable should not have any effect on the throttle cable adjustment.

Agreed 

[Tony Brooks]

5 minutes ago, magnetman said:

I was wondering if the gearbox had momentarily jammed in ahead gear breaking the cable when you tried to shift to neutral. By the time you got to it the prop foul may have dislodged itself. 

 

 

If, and we don't know as we have not been told, this is a hydraulic box then that won't happen, the cable just mores a spool valve. On the other hand, I think it could happen on a mechanical box where a jammed prop may cause "wind up" inside and cause the clutch to jamb. 

 

I am thinking about crude transfer boxes on 4WD vehicle with wind up.

Edited August 12 by Tony Brooks