PSS seal

[martinriches]

I fitted a PSS seal last winter.Did 120 hours with no problems then returning to my berth a horrible grinding noise came from the stern. I put engine into neutral and after 30 seconds got going again. No noise so I thought I must have had something aground the prop. After another half mile same noise so I stopped again waited a few minutes and crept into the marina. I noticed the Seal was hot. I am getting lifted out soon to check things out. I am hoping that I had something wrapped around the prop stopping the water cooling the seal and the noise was either the seal or the cutlass bearing overheating . Anyway I am rambling on here a bit but would such a noise be the result of over heating seal or bearing.

Martin

Martin

 

[greentub]

Last summer in the Med I had a very similar problem. Having spent 12 years in the Med without a problem I had a plague of overheating cutlass bearings resulting in a nasty graunching sound. I hauled out twice over the summer and had to replace 'melted' cutlass bearings. I think I've finally tracked the problem down to a wobble in the shaft. Because my shaft is ovr 6 ft long I have two bearings; one at the shaft exit and one 2/3 rds the way up the shaft. It seems that although both brgs are below the waterline when the bottom one melted it sealed off the water flutes thus affecting the top bearing and seal water flow. The problem of having the two bearings means there is no 'wobble' tolerance. This is my current theory at least. This all pales into insignificance because I've just found out my boat has been damaged in the storms in Marmaris where it's wintering - hey ho! Good luck

 

[vyv_cox]

It sounds like an absence of water. The seal depends on the presence of a very thin film of it. Does the installation have the internal open-ended tube to ensure that water flows through the seal? If not, it is possible to get an airlock in the seal after sailing in boisterous conditions. If it does, check that there is water in it. I occasionally pour fresh water down mine to clear any possible accumulations of salt.

One other possibility is that the rotating face has become pitted, e.g. by corrosion. I noticed that this had happened to mine at the end of the 2007 season. The carbon had worn a bit, throwing debris into the bilge, which was how I noticed it. I reversed the ring and used the other side during 2008, no damage at all at end of season. I have bought a spare ring in case it happens again.

 

[Dave_Rolfe]

Don't suppose you had dried out recently as I seem to remember that the PSS seal needs to be 'burped' to introduce water between the two bearing surfaces to reduce the friction and make the seal.

 

[vyv_cox]

No it doesn't if it has the vent that I referred to in the post above.

 

[pmyatt]

PSS Shaft Seals used-to come in two types, those without water lubrication and those with. Those without are designed for speeds less than 5 knots, and are not manufactured any longer. Any form of "bearing" noise tends to indicate a dry coupling. This usually comes from one of two sources - either a dry bearing from lift-out or similar, or a dry bearing caused by excessive marine encrustation on the seaward side of the bearing.

 

[vyv_cox]

I think you will find that they are all mechanical seal types and therefore are all water-lubricated, by a very thin film between the stainless steel rotating face and the carbon stationary one.

They may be installed in one of three ways:
1. Without any vent or other tubing inside the boat, in which case they will require 'burping' to remove airlocks. This is no longer offered.
2. With a vent tube open inside the boat above the water line. Water passes through the seal and obviates any airlock
3. Instead of a vent tube, water at pressure, e.g. tee'd into the engine coolant supply, is forced through the seal. This is recommended for high speed craft, Mobos and such like.