Water leak.

[Dimond]

Hi All,
I have just put my Mirage26 back in the water for the summer but after a couple of days the bilges are full of water.
I think its coming in from the prop shaft. I have a grease pump which I turn a half turn each time I leave the boat but after taking it out of the water last winter I noticed the grease had turned very thin (watery). I repacked the pump with new grease and have turned it a good few times but as I have said there is a lot of water in the bilge. Now my questions,
(1) Why should it leak so much.
(2) Why did the grease change consistancy
(3) What kind of seal would you expect on this type of prop shaft.
(4) Why and how often should it be changed
(5) Does this need immediate attention or will I be ok until next winter if I keep pumping grease into it.
Answers to any of my questions would be great

Regards
Dimond

 

[Talbot]

In addition to the grease, there should be some proper packing material designed for this job. There will normally be at least three layers , with the cut at the end of each circle being laid 180 degrees apart between layers. The grease then provides the packing between layers. When the leaks start, you squeeze up the packing a bit, and squueze in a bit more grease, eventually there is no more squeeze available, so you just add more grease, eventually you cant add the grease fast enough and the boat sinks !

 

[tugboat]

You say 'I think it's coming from the prop shaft'.
If you have as much water ingress as you suggest, you'll definitely see the stern gland dripping. If not, are you sure the prob is not with your fresh water system? If your boat floats in salt water, tasting the water is a good starting point.

 

[l'escargot]

If it is a straight forward stuffing box and it is the problem, this will give you some idea here. of what is involved.

 

[johnlilley]

Hi There, a possibility...have you got a flexible extension to the stern tube to which the stern gland is inserted, looks like a short length of large diameter car heater hose. It is likely.
These often fail due to grease deterioration and leak on the underside where the rubber splits/goes porus. Check this area for softness, when new it is difficult to squeeze with fingers,. when getting near the end they are soft and supple and slightly bulging. Very common failure points. In an emergency you can wrap a section of thin rubber sheeting around and clip with jubuilee clips to get you home.
John Lilley

 

[LeonF]

I am a rank amateur on things mechanical, but never ASSUME is what I have been taught. It could be a seacock, it could just be a leaky hose. I found water in my bilges after relaunch, coming when I run the engine. Afraid it was the stern gland I watched and saw nothing, could see nothing else leaking. Raising the cockpit sole so I could lie really flat, there it was, a leak from the hose carrying the cooling water into the gear box. Tightened the jubilee clips, but slight leak returned so now have to replace hose. Then found more water in the bilges...and cabin locker.. cold water tank had sprung a leak!! I would dry the bilges completely if possible, then monitor with the engine on and off, with the engine in gear and out, and taste the water if you can bear it..

 

[Dimond]

Thanks for all the replys. I have pushed more grease into the stern gland and it seems to have reduced the amount of water in the bilges. I'm pretty sure the problem is there. Two questions, (1) Can the packing be replaced while I'm in the water and (2) As I said at the end of last season the grease was of a very waterery consistency and there still looks to be some still there. Can anyone tell me why its like this?

 

[Burnham_Bob]

you don't say if you've tightened the stuffing box to recompress the packing. I've never found a reliable way of finding out if the packing is tight enough - most books I've read say to tighten until you get one drip a minute or something like that. Unless anyone on the forum sees why not, I've always tightened my stuffing box after repacking so there is a very, very slight resistance when you turn the propellor with the engine in neutral. Mind you that's with the boat out of the water of course. If you are in the water, see if you can get hold of the prop shaft coupling. That might be an easy way of turning the shaft and seeing how much resistance you've got - it gives you something to grip. If it turns completely freely you could try tightening the stuffing box until you get a very, very faint resistance. There are two nuts on mine that tighten the box and then two locking nuts. I've also always tested the tightness in the water by feeling if the box gets hot to make sure I haven't overdone it

Unless anyone on the forum has real chapter and verse on stuffing boxes I'd try seeing if you need to compress the packing a bit.

 

[Burnham_Bob]

oh and by the way the grease is bound to get watery if your stuffing box isn't tight enough. The grease is in contact with the water in the tube and if water is sloshing around it will wash away the grease.