Heavy vibration
- Thread starter Wiggo
- Start date
nicho
RIP
OK, and thanks for the explanation, but could it be something else causing a misfire, hence vibration? Seems odd that all the alignments in shaft etc seem fine.
oGaryo
Well-Known Member
Wiggo
Well-Known Member
ah, that idea'll not float thenI'll get back in me box
Yeah, off you go, Gary. And don't forget your coat...
After all the injector, pump and fuel issues we've had with that engine, I'm fairly certain I'd recognise engine troubles.
We did appear to be taking significantly more water through the affected stern gland, to the extent that it was a steady stream rather than drips and I tightened it up to get it back to a normal rate.
iangrant
Well-Known Member
Simple thoughts
"I thought it was just the sort of strange feeling you sometimes get in the overfalls at Hurst" ---- Cavitation? But if the engineers satythe prop is OK and the P bracket and seals are alright it can't be the shaft or prop.
FWIW I think if you'd have picked something up or hit something when the vibration started surely the engine would have let you know?
So logically, Props OK, Shaft seal leaking - suspect something here maybe.
Is the shaft still aligned with the gearbox, to check the shaft run a straight edge from a bearer and hold it on the shaft see how much (if) it bobs up and down.
If it moves and let's assume the engine mounts are OK then It has to be something in the gearbox or the coupling? Checking the engine mounts is tricky I had three out of 4 gone before the last one gave up and the whole lump decided to relax onto the engine bearers (92HP Volvo) That really did vibrate!!
Perhaps undo the shaft coupling from the gearbox and check the alignment with a feeler gauge
If it all lines up then it HAS to be a gearbox or engine problem.
Anyway, just a few obvious thoughts
Ian
"I thought it was just the sort of strange feeling you sometimes get in the overfalls at Hurst" ---- Cavitation? But if the engineers satythe prop is OK and the P bracket and seals are alright it can't be the shaft or prop.
FWIW I think if you'd have picked something up or hit something when the vibration started surely the engine would have let you know?
So logically, Props OK, Shaft seal leaking - suspect something here maybe.
Is the shaft still aligned with the gearbox, to check the shaft run a straight edge from a bearer and hold it on the shaft see how much (if) it bobs up and down.
If it moves and let's assume the engine mounts are OK then It has to be something in the gearbox or the coupling? Checking the engine mounts is tricky I had three out of 4 gone before the last one gave up and the whole lump decided to relax onto the engine bearers (92HP Volvo) That really did vibrate!!
Perhaps undo the shaft coupling from the gearbox and check the alignment with a feeler gauge
If it all lines up then it HAS to be a gearbox or engine problem.
Anyway, just a few obvious thoughts
Ian
DAKA
Well-Known Member
you need to go and have a look yourself.
Several years ago when I had the cornich I hooked up a drift net at 25knts, the legs took the full force, oil was bubbling in the water.
On lift out the engineers who claimed to be Volvo Penta authorised said I was lucky and there was no damage, they were lifting it back in.
I knew my boat and I knew it wasnt right so I stopped them and went to look myself, all I could find was a cracked reverse latch which they had missed , they agreed to remove the leg and found the bell housing smashed to bits, top gearbox terminal, total cost of repairs £4-£5000, haven knox johnston paid
When I said rough check of engine alignment turn by hand I meant to turn the shaft by hand, it does not have a lot of grip, turning the props by hand isnt the same.
There is lots of debris between cowes and lymington on the west side, you could have hit something or had a rope round which is now clear.
The flexible coupling could be cracked, I know of an instance where a mooring line round the prop did this, the engineers missed the flexible coupling, 150 nm afterwards the flexible coupling failed, shaft came close to punching hole in the hull and or wrecking the gearbox and shaft almost got wrenched out (leaving 2 inch hole).
Use a black felt tip pen all over the coupling and wipe it off to show cracks.
Check the cutlass bearing for play.
That said your recent injector history should also be investigated, if it has jammed open one of your pots could be fill of diesel with a danger of hydraulic damage.
Hope its nothing serious and just turns out to be a bent prop from debris.
Several years ago when I had the cornich I hooked up a drift net at 25knts, the legs took the full force, oil was bubbling in the water.
On lift out the engineers who claimed to be Volvo Penta authorised said I was lucky and there was no damage, they were lifting it back in.
I knew my boat and I knew it wasnt right so I stopped them and went to look myself, all I could find was a cracked reverse latch which they had missed , they agreed to remove the leg and found the bell housing smashed to bits, top gearbox terminal, total cost of repairs £4-£5000, haven knox johnston paid
When I said rough check of engine alignment turn by hand I meant to turn the shaft by hand, it does not have a lot of grip, turning the props by hand isnt the same.
There is lots of debris between cowes and lymington on the west side, you could have hit something or had a rope round which is now clear.
The flexible coupling could be cracked, I know of an instance where a mooring line round the prop did this, the engineers missed the flexible coupling, 150 nm afterwards the flexible coupling failed, shaft came close to punching hole in the hull and or wrecking the gearbox and shaft almost got wrenched out (leaving 2 inch hole).
Use a black felt tip pen all over the coupling and wipe it off to show cracks.
Check the cutlass bearing for play.
That said your recent injector history should also be investigated, if it has jammed open one of your pots could be fill of diesel with a danger of hydraulic damage.
Hope its nothing serious and just turns out to be a bent prop from debris.
PaulGooch
Well-Known Member
The biggest clue is possibly the water ingress. I'd be suspecting a fouled prop, that subsequently cleared, but has either bent the shaft or damaged the coupling. The shaft now running out of true for either of those reasons will cause both the vibration and the water ingress.
oGaryo
Well-Known Member
shame.. I was poised ready to give you the benefit of my extensive marine engineering knowledge but I guess I'll have to crack on with this BAAAALOOOOOODY DIY instead
RobHom
Active Member
I don't think anyone has mentioned this..... when the boat was out of the water, were the prop blades checked for proper and equal alignment to each other? If you hit a piece of flotsam in the water and it bent or shifted one blade of your prop....it could or would cause a vibration that you could feel with out much trouble.... Doesn't take much of a difference in blade positioning to cause a vibration.... Been there and done that....
Wiggo
Well-Known Member
OK, thanks, guys. I went down yesterday to take a look. The port shaft has been cleaned up, so I take that to be evidence that they ran a dial gauge on it. I'd taken one of my own down but didn't bother using it in the end.
Two things struck me as significant. First, the rear inboard engine mount on the port engine looks to be significantly lower that the starboard engine. This may be nothing at all, as I've never looked at them closely before, but we'll see. Secondly, I decided to clean up the props, and as I was working, I noticed that there is a piece of the shaft about 5mm long aft of the cutless bearing that looks to be polished, much more so than the rest of the shaft (see the photo below)
Is it possible that an engine mount has collapsed allowing the engine and gearbox to shift forward slightly when under load? That would account for the polishing of the shaft by the cutless bearing, and then running on one engine has then allowed the shaft to return to its normal position and making the polished area visible.
I'm down with the engineer on Tuesday, so we'll rotate the shaft, check the alignment and clearances on the flexible coupling. For the sake of it, I'll get the props balanced and checked as well.
Two things struck me as significant. First, the rear inboard engine mount on the port engine looks to be significantly lower that the starboard engine. This may be nothing at all, as I've never looked at them closely before, but we'll see. Secondly, I decided to clean up the props, and as I was working, I noticed that there is a piece of the shaft about 5mm long aft of the cutless bearing that looks to be polished, much more so than the rest of the shaft (see the photo below)
Is it possible that an engine mount has collapsed allowing the engine and gearbox to shift forward slightly when under load? That would account for the polishing of the shaft by the cutless bearing, and then running on one engine has then allowed the shaft to return to its normal position and making the polished area visible.
I'm down with the engineer on Tuesday, so we'll rotate the shaft, check the alignment and clearances on the flexible coupling. For the sake of it, I'll get the props balanced and checked as well.
hlb
RIP
Thats just the problem I had, before the stern gland ripped out. Kept getting it checked, but the fault was not found.
Look and look again at engine mounts
iangrant
Well-Known Member
Agree
Agree with HLB here, if there is movement in the shaft as in the pic then the mounts are very suspect!
When mine gave up hanging on we disconnected the prop shaft, lifted the engine off the mounts with a block and tackle suspended on a pole across the cockpit.
On inspection three of the mounts fell apart and had a real shine between the surfaces, the lat one was just like a clean metal fracture. They had been shot for some time.
Volvo said, "oh yes we fit bigger ones now"
Luckily there was no other damage as the lump just dropped onto the engine beds, I thought it was going to be a load of mess around the shaft gland, bent shaft etc, but no all was OK.
Happy lifting, it's not as dificult as first thought.
Ian
Agree with HLB here, if there is movement in the shaft as in the pic then the mounts are very suspect!
When mine gave up hanging on we disconnected the prop shaft, lifted the engine off the mounts with a block and tackle suspended on a pole across the cockpit.
On inspection three of the mounts fell apart and had a real shine between the surfaces, the lat one was just like a clean metal fracture. They had been shot for some time.
Volvo said, "oh yes we fit bigger ones now"
Luckily there was no other damage as the lump just dropped onto the engine beds, I thought it was going to be a load of mess around the shaft gland, bent shaft etc, but no all was OK.
Happy lifting, it's not as dificult as first thought.
Ian
hlb
RIP
I could have wrote that myself. I had no vibration, just kept getting stern gland leaks.
David of Essex
Well-Known Member
Hi Graham
Have read your problems with a lot of interest, have you have managed to find the cause. Could you keep us informed as we care and would like to know the reason.
David
Have read your problems with a lot of interest, have you have managed to find the cause. Could you keep us informed as we care and would like to know the reason.
David
Wiggo
Well-Known Member
OK, so time for an update. I cleaned the props up and there was no damage at all, but as mentioned earlier, there was a suspiciously shiny bit of shaft either side of the cutless bearing on the port side. The engineer commented that the port prop was very stiff compared to the starboard one, and we wondered if it was because I had nipped up the stern gland too tight.
As a result, I pulled all the packing out of both stern glands and while the port one freed up a little, this made it obvious that the friction was from the cutless bearing. We thought maybe the bearing was shot, but I then went to disconnect the flexible coupling to see if it was a gearbox issue.
As it happened, I couldn't get the coupling undone for want of a suitably thin spanner, but turning the shaft at the coupling showed that the gap between coupling and bolt heads varied between maybe 1-1.5mm and 0mm as the coupling turned, so pretty conclusive evidence of a shaft alignment problem.
At this stage, we can't be 100% on the cause, but the rear engine mounts on the port side look lower than the starboard ones. It all makes a deal of sense: under no load, it looks like the bolt heads in the coupling would just touch, but add the forward thrust on the shaft and they would come into increasing contact with the coupling, and in turn force the coupling to start to hit the gearbox flange, so I think we have found our problem.
As a result, I pulled all the packing out of both stern glands and while the port one freed up a little, this made it obvious that the friction was from the cutless bearing. We thought maybe the bearing was shot, but I then went to disconnect the flexible coupling to see if it was a gearbox issue.
As it happened, I couldn't get the coupling undone for want of a suitably thin spanner, but turning the shaft at the coupling showed that the gap between coupling and bolt heads varied between maybe 1-1.5mm and 0mm as the coupling turned, so pretty conclusive evidence of a shaft alignment problem.
At this stage, we can't be 100% on the cause, but the rear engine mounts on the port side look lower than the starboard ones. It all makes a deal of sense: under no load, it looks like the bolt heads in the coupling would just touch, but add the forward thrust on the shaft and they would come into increasing contact with the coupling, and in turn force the coupling to start to hit the gearbox flange, so I think we have found our problem.
[2068]
...
Main thing is that you are sorting the problem before it turns into the great disintegrating coupling/sterngland/gearbox fiasco.
jfm
Well-Known Member
Yes exactly. Great early diagnosis Wiggo. Might as well change all the engine mounts because if some are gone the others must be near the end of their life? Hope it doesn't eat up too much of your season
hlb
RIP
The solution is. First upgrade engine mounts. In my case from 16mm to 18mm I think.
Mine were forever breaking untill I sunk, then Volvo said, they now recomended uprateing them. So mounts uprated.
This year I again asked engineers to check alignment. As sinking aint much fun. Engineers spent ages and a fortune, trying to realign one engine, which was only a bit out. Finally they got it right by getting a collar made, to fit between gear box shaft and prop shaft. Bear in mind, I live over a hundred miles away, I could only listen to the tale over the phone.
Once the collar was made, it took only an hour or two to get it right. I know because we arrived at the boat, about lunch time and it had been fixed the same day. I can only guess the procedure, but. Once the gear box shaft aligns with the collar and the collar can slide up and down, it must be aligned. Turn prop round and see if it gets stiff. If so, prop shaft bent.. In my case, it was just the difculty of alignment untill the colar was intoduced.
Mine were forever breaking untill I sunk, then Volvo said, they now recomended uprateing them.
So mounts uprated.This year I again asked engineers to check alignment. As sinking aint much fun. Engineers spent ages and a fortune, trying to realign one engine, which was only a bit out. Finally they got it right by getting a collar made, to fit between gear box shaft and prop shaft. Bear in mind, I live over a hundred miles away, I could only listen to the tale over the phone.
Once the collar was made, it took only an hour or two to get it right. I know because we arrived at the boat, about lunch time and it had been fixed the same day. I can only guess the procedure, but. Once the gear box shaft aligns with the collar and the collar can slide up and down, it must be aligned. Turn prop round and see if it gets stiff. If so, prop shaft bent.. In my case, it was just the difculty of alignment untill the colar was intoduced.
aquapower
Well-Known Member
When fitting new mounts keep the engine foot as low down on the thread as possible as this helps to reduce vibration and will also prevent mounting studs from breaking, (this was a major problem on some of the mounts supplied by volvo) It is best to pack the underside of the mount with steel plates if you feel the foot is too high on mount.
aquapower
Well-Known Member
I use a dummy R&D coupling to check alignment, it is a solid steel coupling with the register either side just as the R&D which you bolt to the gearbox coupling and then measure around with a feeler guage and adjust until its correct then undo and fit the R&D, then it should be right.
