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MartinV

Help please - need to understand an engine/prop shaft component

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Hi

 

We're cruising up the Staffordshire and Worcestershire canal and have hit a problem.  When we go into reverse everything is fine but when we go from reverse into accelerating forward again we don't get any forward motion and no movement in the water to show movement. After some time the propeller seems to kick in and we get forward motion again. Very frustrating as, obviously, we don't have control over direction until it does and it was rather windy cruising today.

 

We've managed to get to a boat yard and they found that the bolts on the section I've highlighted on the picture were loose.  After tightening the bolts the backwards and forwards acceleration seemed to work much better. We turned the engine off to fuel up with Diesel and when we went to leave exactly the same thing happened again - we reversed to get off of the mooring and then had no acceleration going forward.

 

Could someone please explain what the part I've highlighted is so that I can search for more info on it as I'd like to have an idea about what they're talking about before we go back tomorrow.

 

Many thanks advance (I really really appreciate any help!)

 

Martin

 

Info:

- The engine is a Yanmar 3YM30.

- I've checked the oil in the gearbox - seems ok

- I've checked the propeller and there is nothing wrapped around it (couldn't feel my arm for 5 mins after mind!)

- Reverse works fine

- The condition appears to be worse after reversing

- Forward acceleration does start but not for a long time after reversing or starting the engine. 

- Once forward acceleration starts again it's fine. We can go into neutral then forward again without problem

 

 

YanmarEngine.jpg

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The piece highlighted is a Centaflex Coupling.

 

http://www.centa-uk.co.uk/

 

Backlash-free transmission of torque and propeller thrust is via a highly flexible rubber element, which is specially designed to reduce noise and vibration within confined spaces. The CF-M dampens torsional vibrations and shocks, eliminates noise and compensates axial, radial and angular misalignments. Additionally, it offers a high degree of electrical insulation.

 

Edited by Ray T

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It sounds like the coupling fitted could be the wrong one, we've had a boat in this week with the same symptoms and the prop shaft needed to be replaced along with the correct coupling installed and tightened properly.

The good news is that it's far cheaper fix than the gearbox it protects. 

Edited by matty40s

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Ray

 

Thanks so much for this!! It's come flooding back with that one word.  I remember that the guys at the yard explained that forward acceleration pushes against the centraflex and reverse pulls against it. The bolts were loose and have been tightened but if it's still happening then the rubber in the center may be damaged.

 

We've been through a lot of low water areas in the last few days and I'm wondering if this has contributed to the problem? 

 

Thanks for the info -I'll go and have a read

 

Martin

 

2 minutes ago, matty40s said:

It sounds like the coupling fitted could be the wrong one, we've had a boat in this week with the same symptoms and the prop shaft needed to be replaced along with the correct coupling installed and tightened properly.

The good news is that it's far cheaper fix than the gearbox it protects. 

Matty

 

Thanks for the reply - the boat has been fine for two years+ but I really don't have a clue to be honest.  We'll go back over tomorrow and see what they can find.  Excuse my ignorance but does this require the boat to come out of the water?

 

Thanks

 

Martin

  • Greenie 1

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Yes, if you've been putting major load on the shaft because of continuous mud dredging,  then it could well have damaged the coupling. .....so it may well be the right one, but knackered.

If it's only the coupling, you can do it in the water, if the prop shaft is badly worn then it's an out of waterfix

Edited by matty40s

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Just now, matty40s said:

Yes, if you've been putting major load on the shaft because of continuous mud dredging,  then it could well have damaged the coupling. .....so it may well be the right one, but knackered.

Sounds very probable - the water levels have been very low from Stewpony lock upwards.

3 minutes ago, matty40s said:

Yes, if you've been putting major load on the shaft because of continuous mud dredging,  then it could well have damaged the coupling. .....so it may well be the right one, but knackered.

If it's only the coupling, you can do it in the water, if the prop shaft is badly worn then it's an out of waterfix

Matty

 

Thanks - fingers crossed. Thank-you very much for the information - I really value the responses!

 

Cheers

 

Martin

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I think that they fit to the shaft by a sort of clamping ring, You shove the shaft in to the coupling then tighten up the bolts and it clamps the shaft really tight. (Others may know better) Chances are that there is now wear in the shaft end and / or the clamping ring / hub bit of the centaflex  A few thou is enough to render the thing useless. I could be wrong. The fix is a new part from Centaflex (just the clamping part) and if you have enough shaft to pull a bit in from outboard cut the scored and damaged bit off the end of the shaft and re fix it all but do the bolts / grubscrews up nice and tight.  That's my guess without looking at it, I'm not too familiar with these. Its not a disaster but if the shaft is ever so nearly but not quite long enough to cut an inch off you may find a few washers or spacers between the gearbox / coupling give you just a bit more length. You may just have to take the shaft out and get it turned down from (e.g.) 1.5 inches to 1.25 and an appropriate hub clamp. Others will know more about these couplings.

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13 minutes ago, Bee said:

I think that they fit to the shaft by a sort of clamping ring, You shove the shaft in to the coupling then tighten up the bolts and it clamps the shaft really tight. (Others may know better) Chances are that there is now wear in the shaft end and / or the clamping ring / hub bit of the centaflex  A few thou is enough to render the thing useless. I could be wrong. The fix is a new part from Centaflex (just the clamping part) and if you have enough shaft to pull a bit in from outboard cut the scored and damaged bit off the end of the shaft and re fix it all but do the bolts / grubscrews up nice and tight.  That's my guess without looking at it, I'm not too familiar with these. Its not a disaster but if the shaft is ever so nearly but not quite long enough to cut an inch off you may find a few washers or spacers between the gearbox / coupling give you just a bit more length. You may just have to take the shaft out and get it turned down from (e.g.) 1.5 inches to 1.25 and an appropriate hub clamp. Others will know more about these couplings.

Thanks - it's all making a bit more sense now - at least I won't feel completely in the dark when I speak to the engineers tomorrow!

 

Martin

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If the shaft and the inside of the coupling clamp are badly score and worn, a strip of drinks can between the 2 will get you going for zero cost.

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Martin, it certainly sounds like a coupling problem, but it'd be a shame to go to the bother of changing it if it's not!  I've read through the above and I can't see any reference to the first, simple check you should do.  Looking at the coupling, do both sides of the shaft turn together at the same speed?  If the gearbox end is turning and the prop end isn't following it in unison whatever the gear or revs, it's definitely the coupling.

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Which bolts did the yard tighten? There are two sets, one which is nuts on studs at the gearbox output flange end and bolts at the prop end.  The prop end ones need to be really tight and done up in the right order.   I would have another go at getting these ones done up properly.  Don't overtighten the ones at the gearbox end though - these are steel studs threaded into alloy so will strip easily.

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Put a chalk or felt tip pen mark on the shaft and one on the back of the coupling inline with each other, then go backwards and forwards a few times to see if the marks still align up.

  • Greenie 2

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5 hours ago, Nobag said:

I had a similar problem last year and a gearbox oil change solved the problem. 

May well do on a hydraulic box but the photo seems to show a mechanical one. My mechanical gearbox worked with no oil so seems a bit unlikely.

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9 hours ago, Sea Dog said:

Martin, it certainly sounds like a coupling problem, but it'd be a shame to go to the bother of changing it if it's not!  I've read through the above and I can't see any reference to the first, simple check you should do.  Looking at the coupling, do both sides of the shaft turn together at the same speed?  If the gearbox end is turning and the prop end isn't following it in unison whatever the gear or revs, it's definitely the coupling.

Check the that the gear cable is pulling (or pushing ) the gearbox lever the correct amount. If you disconnect the cable from the gearbox,you can check that forward and reverse are working by operating the lever by hand.

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Everyone,

 

Thanks so much for the replies! I'm always amazed at how generous everyone is with their time, advice and information!

 

I'm really sorry for a lack of speedy reply but we took the boat back today and after we were sorted we had to move up to a new mooring so I haven't been able to get on the computer.

 

So...

 

We took NB Jambo back to Oxley Marine on the Staffs & Worcs this morning and they have been absolutely amazing.  We were hoping yesterday after they tightened the bolts on the Centaflex (which were very loose) that everything would be sorted but as we moved away to moor on the opposite side of the canal last night (it was getting dark) the problem reappeared and again we weren't getting any forward acceleration (during testing whilst moored up at their yard it had been absolutely fine). 

 

So as we crept over the width of the canal this morning back to their side of the bank we still thought the problem was with the Centaflex but after closer inspection it was discovered the problem was actually with the gear box (at which point my heart sank as you can imagine).  It turns out, despite researching on the net and getting what I thought were the correct answers, I had overfilled the gearbox oil which had led to the forward gears becoming smooth and slippery!  

 

Dave (from Oxley Marine who is an absolute legend!) found on checking the gearbox that not only was it too full but that the oil in there was not a healthy colour at all. After multiple cleanouts with diesel though the colour started to lighten and we started to get some normality to the gearbox. In reality the gearbox is pretty shot but thanks to Dave's ministrations and by mixing the ATF oil with 50ml of diesel we're able to keep on for hopefully a while longer (hopefully long enough to save up for a new gearbox!!).

 

I can't recommend Oxley Marine enough - they're genuine, fantastic people who wanted to help and keep us running and lots of other people who we'd met on the way up the Staffordshire Worcestershire canal had also been saying really positive things about them.

 

All the best and thanks for all your replies

 

Martin

 

  • Greenie 2

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I'd endorse that recommendation from personal experience, very helpful. 

Glad you're sorted. Is that Jambo that used to be in Victoria basin until recently?

 

Edited by sharpness

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18 minutes ago, sharpness said:

I'd endorse that recommendation from personal experience, very helpful. 

Glad you're sorted. Is that Jambo that used to be in Victoria basin until recently?

 

Yup - that's us ?

 

We left the mooring last September and we are spending the year cruising around the country having a great time (when the engine isn't freaking us out).

 

Martin

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Yeah - that's what we learnt as well ? 

 

She was named that when we moved onto her and the previous owners said they often had people calling the name out as they passed (they were living in and around London)

jamboheader2.jpg

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12 hours ago, MartinV said:

the previous owners said they often had people calling the name out as they passed 

We had the same with Wot Ever...

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50 minutes ago, WotEver said:

We had the same with Wot Ever...

Not for exactly the same reason!

I might register mine in T.W.A.T. oops, just googled that!

I might have to have a re-think, weep.......

Edited by LadyG

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16 hours ago, MartinV said:

We took NB Jambo back to Oxley Marine on the Staffs & Worcs this morning and they have been absolutely amazing.  We were hoping yesterday after they tightened the bolts on the Centaflex (which were very loose) that everything would be sorted but as we moved away to moor on the opposite side of the canal last night (it was getting dark) the problem reappeared and again we weren't getting any forward acceleration (during testing whilst moored up at their yard it had been absolutely fine). 

 

It turns out, despite researching on the net and getting what I thought were the correct answers, I had overfilled the gearbox oil which had led to the forward gears becoming smooth and slippery!  

 

Dave (from Oxley Marine who is an absolute legend!) found on checking the gearbox that not only was it too full but that the oil in there was not a healthy colour at all. After multiple cleanouts with diesel though the colour started to lighten and we started to get some normality to the gearbox. In reality the gearbox is pretty shot but thanks to Dave's ministrations and by mixing the ATF oil with 50ml of diesel we're able to keep on for hopefully a while longer (hopefully long enough to save up for a new gearbox!!).

 

 

There is something here that makes no sense to me (apart from the fact the OP says gears and I think they mean clutches). I fail to see how a properly vented overfilled box will make the clutches, be they cone or multi-plate, too slippery. I can see that very badly emulsified oil that had formed a grease like consistency could.

 

If anyone can give a definitive explanation I would very much like to learn.

 

Anyway, very pleased its sorted

Edited by Tony Brooks

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On 08/02/2019 at 20:25, MartinV said:

Hi

 

We're cruising up the Staffordshire and Worcestershire canal and have hit a problem.  When we go into reverse everything is fine but when we go from reverse into accelerating forward again we don't get any forward motion and no movement in the water to show movement. After some time the propeller seems to kick in and we get forward motion again. Very frustrating as, obviously, we don't have control over direction until it does and it was rather windy cruising today.

 

We've managed to get to a boat yard and they found that the bolts on the section I've highlighted on the picture were loose.  After tightening the bolts the backwards and forwards acceleration seemed to work much better. We turned the engine off to fuel up with Diesel and when we went to leave exactly the same thing happened again - we reversed to get off of the mooring and then had no acceleration going forward.

 

Could someone please explain what the part I've highlighted is so that I can search for more info on it as I'd like to have an idea about what they're talking about before we go back tomorrow.

 

Many thanks advance (I really really appreciate any help!)

 

Martin

 

Info:

- The engine is a Yanmar 3YM30.

- I've checked the oil in the gearbox - seems ok

- I've checked the propeller and there is nothing wrapped around it (couldn't feel my arm for 5 mins after mind!)

- Reverse works fine

- The condition appears to be worse after reversing

- Forward acceleration does start but not for a long time after reversing or starting the engine. 

- Once forward acceleration starts again it's fine. We can go into neutral then forward again without problem

 

 

YanmarEngine.jpg

A lovely clean engine and engine bay. Looks an easy area to keep clean and tidy. Am green with envy. To get at my engine requires me to get into more positions than are listed in "Kama Sutra" and I have given up trying to clean the engine bay out.

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