Prop shaft wobble through dripless shaft seal

[penfold]

For my money that's bent, not misaligned, but without using a dial gauge it's just guesswork; either way it needs investigation by a competent marine engineer given you're asking questions on here. The risk of continuing to run as-is is faster wear of the dripless seal and cutless bearing and a need to check the tightness of the coupling fasteners regularly and often.

 

[vyv_cox]

I was having a good look at the engine running tonight, and noticed that there is some wobble where the prop shaft enters the dripless shaft seal.

The engine itself doesn't seem to be misaligned particularly, but maybe the prop shaft isn't quite straight.

How much wobble is too much wobble? ?

Video:

Not sure what has been changed but it appears that the shaft may not be central in the coupling. It may be that the two coupling halves have been separated and replaced in new positions. You can check easily, ideally with a dial gauge on the gearbox but a simple pointer clamped somewhere should be enough. Turn the engine over in gear with the starter motor, or with a spanner if possible.

 

[tjbrace]

My Volvo drip less seal seems to have a ‘supporting role’ too. OK for the past 16 seasons. A little grease and a burp at the start of the season isn’t too onerous.

 

[MattS]

Thank you all for your replies. As I’m sure many of you do, I use Ybw to try and learn from other experienced boaters, and triangulate the many different opinions out there ? if there were a single clear answer for these things, it would be much simpler but of course that’s not how boating works!

@Graham376 Thanks - just having a pointer on relative urgency of the problems is useful. Exhaust is definitely getting fixed ASAP.

The OP suggests using the engine once a week. This can be an hour or 8 hours so one is still not sure of use. Personally, I would just keep an eye on it if only a few hours & then get it fully sorted on dry land at the end of the season. It will not be catastrophic provided it is checked each week for drips on the seal & even then a jubilee clip round it in emergency would help until the boat was bought ashore

@Daydream believer I’m only using as an aux for local sailing trips, so no more than a few hours on a day trip. But my main concern was that I have work scheduled in Suffolk end August, and need to take her up from the Medway - so was trying to get a frame of reference as to whether I could wait until then when she’ll be hauled out anyway. Thanks for the jubilee clip tip - I’ll make sure I’ve got one spare on board that’s up to the job just in case.

You have identified an issue and have been advised that it is significant, perhaps you should deal with it now instead of waiting later as damage usually just gets worse if left to its own devices. At a guess, perhaps your insurance requires you to make good damaged once identified.

@BlowingOldBoots Thanks - yes - I intend to deal with it as soon as I can. I’m quite a risk averse person hence why I sought opinions as to how much of a concern this should actually be.

If this is in a Moody then the only real bearing surface is the cutless in the P bracket. With the amount of wobble you have that bearing will wear more rapidly - it may even already be worn which accentuates the wobble. The Volvo seal seems to be taking the movement OK, but the lip seals may wear more quickly and lead to water leaking past. Good idea to apply extra grease to the seals if continuing to use the boat. Doubt anything will fail catastrophically with a few more hours use so keep an eye on it.

@Tranona Yes - it’s a Moody 28. Thanks for the tip re grease - I have a new tube of Volvo grease and a plastic straw ready to go for next trip down to the boat.

If my interpretation is correct you have two threads running at the moment, this one and a porous exhaust.

If it was me I'd get the boat lifted today work on her over the weekend and splashed on Monday, if you have the skills for a DIY fix, or find somebody who will give you a firm commitment to do the work over the weekend or next week.

I‘m not experienced with the mechanical side, so wouldn’t attempt DIY at this stage. unfortunately there’s quite a wait on lifting at my marina, so no option to get lifted out straight away. I’ll be trying to book a lift out asap.

I have a local beta engineer who I'm hoping can take a look at it, so will be trying to get a plan together with him tomorrow. He’s already on the case ordering me in a new injection elbow so fingers crossed that can be sorted pretty soon,

To the OP, Is this boat new to you?

If it is i'd want to get a professional to have a look around the engine and fittings before going any further. Looking at your three threads on here is making me concerned for your understanding of marine mechanics. No offence intended (I'm learning myself) but wouldn't want you to go out and get into trouble.

@Gixer Ive had her since last October, but she’s only been launched since May this season.

I’m most definitely seeking professional help with these - I can’t solve these things myself. My engineer already has parts on order to replace the exhaust injection elbow.

But as you’ve mentioned everyone has to build up this knowledge somewhere, especially if they haven’t encountered the problem before. i use these forums very much to learn from more experienced and knowledgable boaters about these problems so that I understand what’s going on and what next steps I need to be taking, and I’d hope that was seen as a positive thing generally! If anything it’s getting this help that will likely stop me taking risks out of ignorance.

Not sure what has been changed but it appears that the shaft may not be central in the coupling. It may be that the two coupling halves have been separated and replaced in new positions. You can check easily, ideally with a dial gauge on the gearbox but a simple pointer clamped somewhere should be enough. Turn the engine over in gear with the starter motor, or with a spanner if possible.

Looking closely at the coupling when running it up in the marina today, I actually think there’s visible misalignment of the coupling itself as it spins round - so I think this could well be the case.

I did have the engineer put a bonding wire on across the R&D, which would have required him to undo and re-tighten two of the bolts, and I am wondering if that could have put things out..

 

[Gixer]

@MattS I've had my boat 10 years and still find myself asking loads of questions Glad you're getting professionals to take a look.

My understanding in boat mechanics, plumbing, electrics and now fuel systems has sky rocketed since being on here. Keep the questions coming there's some seriously knowledgeable people on here.

 

[MAURICE]

if the engine mounts seem Ok and allignment seems good. First i would check the shaft cutlass bearing isnt worn before doing anything else.

 

[Daydream believer]

@MattS Keep the questions coming there's some seriously knowledgeable people on here.

Certainly the level of debate gets a bit serious sometimes

 

[Rhylsailer99]

after reading these comments and looking into all the boats that have almost sunk or have sunk i will stick to my packing gland that just lets out the odd drip now and then .

 

[MattS]

after reading these comments and looking into all the boats that have almost sunk or have sunk i will stick to my packing gland that just lets out the odd drip now and then .

Would you mind helping me understand this comment @Rhylsailer99? I don't follow I'm afraid! Is this because you feel the dripless glands are at more risk of failure? I'd presumed that a traditional packing gland would be just as damaged / susceptible to issues from shaft wobble (if not more as they're not flexible...) - but that might have been the wrong assumption!

 

[Gixer]

For what its worth I've just bought a shiny new PSS seal to replace my old packing box.

 

[Rhylsailer99]

Would you mind helping me understand this comment @Rhylsailer99? I don't follow I'm afraid! Is this because you feel the dripless glands are at more risk of failure? I'd presumed that a traditional packing gland would be just as damaged / susceptible to issues from shaft wobble (if not more as they're not flexible...) - but that might have been the wrong assumption!

I did some research and when a modern dripless gland fails it can b let water in fast but a traditional packing gland tends to just drop more and gives your bilge pumps chance to keep up.