Hi all

In need of some advice.

Splashed yesterday after two days on the hard having the old stuffing box removed and dripless seal installed. All good, no drip whatsoever.

Prior to the boat coming out, I was very fortunate to have an almost completely dry bilge.

Since relaunching yesterday, though, I am making water somewhere. Not dangerous quantities but enough to annoy me and trip the float switch every few hours.

I think it may be entering at the skin fitting for the speed transducer. I had the blank plug in, not the paddlewheel.

The forward sling was covering the transducer. When I commented on this to the travelift guys, they said it was only the canvas cover, not the sling webbing itself on the transducer and assured me it would be fine.

Thoughts???? Advice?????
Thanks in advance.

I swapped the speed transducer plug for the paddlewheel two weeks ago which started leaking. Looks like it was suppose to have two O rings, however only one was present. Ended up coating the plug O ring will liberal amounts of grease and that stopped the leak. I used a lanolin based grease that I use for the batteries, but I believe any thick grease on hand will do. Checked a week later and the bilge was completely dry. Will add another O ring next month when the yacht is out of the water, looks like only one O ring has been in the plug for years.

Hope this help.

Ilenart

I would suggest permanent marks on your toe rail where the travel lift strops should go to avoid this sort of thing next time.

did someone burp the stern gland when it went back in the water before starting to spin the prop ?

Ok great that it's not the transducer skin fitting or the internal plug into it leaking. That's good news.

But not good news is that saltwater is coming in still, and that it seems to be "pretty much at the waterline". Sorry to say but if you have water coming in to around the waterline level and the float switch is not tripping then the float switch is set way too high - it should be down in the bilge way lower than the normal waterline and has to trip and activate the pump way before the waterline level. Please clarify this so we can know?

So where is it leaking? Seems like more talc powder tests are needed.

But also more yacht details would be useful to try and diagnose this issue remotely. So I see you have a Mottle 33 which is probably 1980s build? What are all the hull skin fittings and entries - are they all bronze fittings (needed) or are some plastic? How old are they all? Besides the speedo skin fitting assume you might have inlet and outlet loo fittings (unless blocked off to change to a portaloo system - but the "blocked off" old fittings could still be a source of problem), sink skin fitting, diesel cooling water inlet skin fitting, prop shaft stuffing box, and rudder through hull up to deck system. Probably more - please advise.

So if the new stuffing box is all working fine then another skin fitting or the rudder system is under the microscope - assuming your keel bolts and associated hull structure are all sound. Have you had any altercations with sandbanks or worse lately. Sorry to go to the worst case scenario.

The rudder stock should go through the hull skin and then up to the deck exit, with appropriate bearings and hull and deck structure, also a large diameter grp tube surrounding the stock and the hull and deck bearing assemblies so that if the hull bearing became a bit worn the tube would contain the water ingress.

The fact that the leak seems to stops at a certain level is maybe a clue - maybe something is tightening up with water ingress and ceasing the leak.

Appreciate response to the above, and more, and we all should be able to solve this for you.

cisco said..
If the only thing you changed during the slipping is the stern gland and now you are taking water the logical place to look is the stern gland.

Check to see if you are making water with the engine running.
Also sometimes water can lay in hidden areas. When the boat is lifted, there can be a change of level or a swing of inertia in the slings that shifts the water to a different place or finds its way to the bilges

SV Wavesong said..
Thanks all for your help.

After another emptying and sponging of the bilge, it now remains dry. Hopefully this will continue. I am still confused but very relieved.

That's good to hear. Always nice to find out the source though. I notice you mentioned a float switch. When that fails consider installing a Waterwitch. These have no moving parts but most importantly can be mounted very low. They are expensive.

www.whitworths.com.au/swch-waterwitch-mini

Ramona said..

SV Wavesong said..
Thanks all for your help.

After another emptying and sponging of the bilge, it now remains dry. Hopefully this will continue. I am still confused but very relieved.

That's good to hear. Always nice to find out the source though. I notice you mentioned a float switch. When that fails consider installing a Waterwitch. These have no moving parts but most importantly can be mounted very low. They are expensive.

www.whitworths.com.au/swch-waterwitch-mini

Thanks Ramona. I think it would be $100 well spent.

If you want a mostly dry bilge you need a small pump sump. The suction of the pump needs to be covered with water, otherwise it sucks air. A sump does this, so the rest of the bilge can be dry. A float switch in that small sump will match the pump. There is also the problem of the little bit of back flow when the pump cuts out, so the float switch needs a differential between cut in and cut out.

It is amazing how hard it is for some people (including engineers) to understand the concept of having a little sump. (This is personal, I have been battling for 20+ years to get the message across in my field.) My current boat does not have one in the bilge, so it is back to the "hi-tech" sponge.

SandS said..
did someone burp the stern gland when it went back in the water before starting to spin the prop ?

+1.

Changed my prop recently, and got a steady, running drip until we burped the seal. However, I didn't do it until after I had motored back to the mooring (5 - 10 min under motor). Since then, all dry.

By "burping", I mean keep squeezing the soft rubber outer until you get the air out, or until it stops dripping.

"Burping is apparently not required with the Volvo dripless seal he installed."
That goes against the many, many, times I have read that burping a Volvo seal is needed. However, it is simple engineering. Take a look for yourself.

The seal is a closed pocket with internal ridges which form the seal against the shaft. It needs water on the rubbing surface to provide a little lubrication and cooling. Some mechanical seals have a hose connected to the cooling water circuit which provides the lubrication/cooling. The original Volvo seal does not have that, and the burping is to get rid of any air pocket in the seal, so the water level can rise into it. You just have to squeeze it.

If it is hard to get at, one of those long handled tongs that are used to pick up things on the ground without bending over, could help.

Yara said..
"Burping is apparently not required with the Volvo dripless seal he installed."
That goes against the many, many, times I have read that burping a Volvo seal is needed. However, it is simple engineering. Take a look for yourself.

The seal is a closed pocket with internal ridges which form the seal against the shaft. It needs water on the rubbing surface to provide a little lubrication and cooling. Some mechanical seals have a hose connected to the cooling water circuit which provides the lubrication/cooling. The original Volvo seal does not have that, and the burping is to get rid of any air pocket in the seal, so the water level can rise into it. You just have to squeeze it.

If it is hard to get at, one of those long handled tongs that are used to pick up things on the ground without bending over, could help.

Hi Yara


I'm just going by what the mechanic informed me. He's a very established operator in the area and swears by the Volvo seal over the PSS.
There is a tube of blue grease which comes with the seal. I need to insert some into the seal every 6 mths.

Cheers

also , another caution with these type of seals is when water blasting crap of the hull be very careful not to blast crap up the stern tube . as when relaunched the rubbish will be pushed up into the sealing fins , get caught in the grease and trash the seal

the Volvo Penta shaft seals are definitely meant to be burped, you can read it for yourself in the installation guide available here:

www.generalpropeller.com/Volvo-Shaft-Seal

at minimum you want to do this whenever the boat comes out of the water. you just need to squeeze the seal until some water squirts out.

SV Wavesong said..

SandS said..

Yara said..
"Burping is apparently not required with the Volvo dripless seal he installed."
That goes against the many, many, times I have read that burping a Volvo seal is needed. However, it is simple engineering. Take a look for yourself.

The seal is a closed pocket with internal ridges which form the seal against the shaft. It needs water on the rubbing surface to provide a little lubrication and cooling. Some mechanical seals have a hose connected to the cooling water circuit which provides the lubrication/cooling. The original Volvo seal does not have that, and the burping is to get rid of any air pocket in the seal, so the water level can rise into it. You just have to squeeze it.

If it is hard to get at, one of those long handled tongs that are used to pick up things on the ground without bending over, could help.

Yes , if it has no additional water cooling , the rubber seal will run dry as the air pocket is created when going back in the drink. those seals also require rubber grease at regular slip intervals to lube the little sealing fins inside the seal . this is type i,m on about ,this one must be burbed on entry to water ,before spinning the prop !

Thank you Sands

your welcome

Jolene said..
I had a look at a boat yesterday that was leaking water into the bilge. The owner had washed the bilge out and sponged it dry only to return the next day to find water in the bilge. He mopped up and then later in the day found water again.
I had a look at his bilge pump and found that the anti drainback valve slightly leaks and is basically dumping the contents of the bilge hose back into the boat over the period of a few days. It was a brand new Rule type pump with the anti drain back valve. The valve is similar to a joker found in the Jabsco sea toilets.

Just a thought, if you put some food die into the water in the bilge (making sure it wont stain anything first) pumped it out, sponge it dry, if it was running back from pump / hose you would know due to the colour, if it was clear you can then hunt for the leak else ware.