prop shaft leak

[Dave Bebb]

Hi all prop shaft is dripping when run after about 30 mins put some grease in then it stops , when it starts dripping and i get in the engine bay and stand on the gear box to get down to the shaft to put some grease in it stops ,when i take my foot off the gear box it starts dripping again until i put a bit of grease in again . ps it the type you put the blue silicon grease in . not a stuff box .do you think it the engine mounting nuts need lowering a 1 or 2 mm or not .  thanks 

 

Edited June 24, 2017 by Dave Bebb

[WotEver]

I'd agree with your diagnosis if it were my boat - it definitely sounds like the alignment is slightly out - but best to wait for an expert as they may say that it's more likely to be wear on the shaft and moving it slightly is only a temporary fix. I don't know those seals well enough myself. 

[blackrose]

8 hours ago, Dave Bebb said:

 ps it the type you put the blue silicon grease in . not a stuff box .

 

Are we talking about a water-lubricated stern gland or a traditional greasy gland? 

Edited June 25, 2017 by blackrose

[Tony Brooks]

"Getting down to put the grease in" makes me suspect its a Vetus packless gland.

If so has the OP read the VETUS (not the builder's nor vendor's instructions or even well meaning replied on here in respect of routine servicing. If not please do so. It might be scale on the shaft, a worn seal (coupling off to replace seal) or as the OP says the engine being out of line. However as the Vetus seal is flexible and as far as Vetus are concerned is paired with a Cutless shaft bearing there is a degree of compliance in the system that should allow for minor misalignment.

If it is not a Vetus gland the above has no relevance so please identify or post a photo.

[dor]

If it is Vetus gland it shouldn't drip at all. Mine has done over 3,000 hours with no problem.  However shaft misalignment can cause uneven wear on the lip seal which will cause it to drip.  Not giving them a squirt of grease once every 100 hours or so can also lead to wear.  It is fairly easy to replace in the water, but the cause needs to be identified.

It can be caused by excessive wear on the propshaft; if you can, try and move the propshaft inboard and see if there is a groove on the shaft.  This can result from the bearing running dry.  Also there should be a pipe running from the top of the bearing, usually into the weed hatch box.  Sometimes these are fitted with a lever valve.  The pipe is to allow air to escape so that the bearing can be flooded, if it is blocked this can lead to excessive wear.

[Dave Bebb]

Yes it is a Vetus with a air pipe coming out she is going in for bottom blacking this mouth so i will ask the them to change the seals ,thanks for all your replies  

[bizzard]

Although the seal maybe worn, by standing on the gearbox stops the leak it might need re-aligning or lowering a touch. Or the mounting rubbers have become soft and pappy and standing on the box might be damping excessive movment of the engine and box which stops the leak.