PSS shaft seal or something else

[Steve_Sigma33]

I have a PSS shaft seal on my Sigma 33 that is perfectly fine when the engine is at rest or running up to 1800 revs but if I go above 1800 it starts to allow water in. Checked the collar and the graphite core and they are not stuck together or any obvious signs of dirt in between the two. Is it a case I need to adjust the collar or should I be looking at engine mounts etc?

I should state the boat didn’t get a huge amount of use last year but this only became evident when we went out for a play a few weeks ago.

All advice welcome.

 

[doug748]

They cope pretty well with a certain amount of misalignment.
If it looks to be running true at 2000 rpm things may well be ok. If it's all a bit of a blur then your engine mounts could be at fault. I had some leakage once and found the engine was only supported on three mounts. First clue was vibration at tickover that I had not noticed before.

If your shaft is 1in or so then the bellows should be compressed by 3/4in. If the access is good you can check this on the water but it involves a bit of water coming in as you have to pull back the rotor to start with.

.

 

[Steve_Sigma33]

Thanks Doug

access is possible with a bit of an inversion and a wiggle. It is a1 » shaft so I think I will brave undoing the collar and check it is at 3/4 ». My only big concern is getting the grommets to undo. I think they’re 3mm alum bolts but I’ll need to take my lenses out so that I can see up close!! I hate getting older!

I will certainly check all the mounts are tight to make sure the engine is as steady as possible. I think she is probably steadier at higher revs than tickover but worth a tweak to be sure. Ideally I want to resolve this before coming out of the water rather than making the boat look pretty and then find she needs hauling out again!

 

[doug748]

There are two sets of allen screws - two screws in each hole. The idea is the second screw locks the first in position (unless someone has lost some, of course). Officially you should not re-use the screws as they have a head that deforms but I have done it and lived to tell the tale. If this concerns you, you can always put a jubilee clip on the shaft, behind the rotor, as a back up. In fact a second jubilee clip say 1/2 in behind the first gives you an instant check to see if the rotor has ever slipped. You can arrange the knuckles so as to balance the shaft.

Good luck with it, working in confined quarters does not get any easier as time passes.

.

 

[Lightwave395]

I installed my first ever PSS seal yesterday (1.25" shaft) and did think a jubilee clip would be a good idea. Hopefully it's in all fitted correctly, however I'm looking forward to launch in March with slight trepidation !

 

[Malish]

Vyv's site is a useful library of stern gland information:

Stern glands

 

[Gixer]

I had one fitted last year professionally. Its on a 1gm (single cylinder) which bounces around like a crazy thing.
Not had a drop of water in the bilge from the seal..

 

[superheat6k]

I use a long hanger nut on a piece of threaded bar, or long bolt to load the seal. Once you know the unloaded distance between the seal and the shaft coupling face, cut a piece of studding to fit the gap less 3/4 of the length of the hanger nut, put the bar against the seal and unwind the nut whilst holding the stud still either with mole grips of a couple of locked nuts.

Mark the shaft in the starting position so you can measure the compression distance.

 

[mikegunn]

I have a PSS shaft seal on my Sigma 33 that is perfectly fine when the engine is at rest or running up to 1800 revs but if I go above 1800 it starts to allow water in. Checked the collar and the graphite core and they are not stuck together or any obvious signs of dirt in between the two. Is it a case I need to adjust the collar or should I be looking at engine mounts etc?

I should state the boat didn’t get a huge amount of use last year but this only became evident when we went out for a play a few weeks ago.

All advice welcome.

Is your PSS seal fed with water from the engine’s raw water pump? If so, it may be being fed with more water than can easily escape via the cutlass bearing at high engine rpm. Try reducing the water flow by throttling (squeezing) the feed pipe, which I presume is a rubber compound. If water ingress stops, the solution will be to effect a permanent reduction in flow. The seal only needs sufficient water to lubricate the interfaces.

Mike

 

[Steve_Sigma33]

Is your PSS seal fed with water from the engine’s raw water pump? If so, it may be being fed with more water than can easily escape via the cutlass bearing at high engine rpm. Try reducing the water flow by throttling (squeezing) the feed pipe, which I presume is a rubber compound. If water ingress stops, the solution will be to effect a permanent reduction in flow. The seal only needs sufficient water to lubricate the interfaces.

Mike

Hi Mike, not fed from the engine. Simply clamped on to the stern tube and has a breather pipe. The jubilee clips on the breather pipe have corroded and will be replaced. I will also check the breather pipe is not blocked but I can’t see how that would happen. Will be part of my next trip behind the engine.

 

[mikegunn]

Hi Mike, not fed from the engine. Simply clamped on to the stern tube and has a breather pipe. The jubilee clips on the breather pipe have corroded and will be replaced. I will also check the breather pipe is not blocked but I can’t see how that would happen. Will be part of my next trip behind the engine.

Well, hopefully it may just be a blocked vent tube. If not, the most likely cause would be that the rotor's face is not absolutely square to the shaft's axis. That could result in the static member being unable to react quickly enough at higher shaft speeds to follow the swash of the rotor as it rotates. An effective gap could then form between the static and rotating members which equates to the runout of the rotor. If your boat is in the water it'll be a little difficult to measure the runout of the rotor's face, even if you can access it easily. Dependant on the severity of water ingress it might be easier to live with it and resolve the problem during your next lift-out.

Mike

 

[vyv_cox]

When PSS seals are left a long time it is possible for the stainless steel face to suffer corrosion. There is a pic of one on my website under crevice corrosion. I am not sure how this could account for your symptoms but worth checking. Otherwise I would suspect bellows loading too low.