Sureseal series 1

[lumphammer]

I am about to fit this seal to a new propshaft. I would have used a volvo seal however the diameter of my stern tube was too big.

I have a question about the water cooling feed. This is supposed to be connected to a take off on the cooling water system. Where in the system is the best place to connect to?

On a small yacht do I need the forced cooling, would it be enough to take the feed tube up above the waterline and just let the water flow through the cutlass bearing do the cooling?

And finally, always a dangerous question after you have made the decision and bought the product, is there anything I need to be aware of when fitting?

 

[Guest]

The feed must be above the water line and in the antisiphon section. If it is below the waterline on either of the sides then there will be a direct line from the sea to either the engine water pump or the exhaust system. Either way it is unsafe. The best position is the engine pump side and above the water line at all times.

As for not providing water supply. It depends on the heat generated by the seal. This is not insignificant.

Also there is the issue of dirt. The flow of filtered water out of the shaft will help it stay clean and reduce wear from large items. However, the filters on engines do not get out the grit so continual pumping of silt through the seal and bearing is not good.

No idea on the long term pros and cons but it will depend on the manufactures recommendations for your shaft speed.

However, I have sorted out 2 engines in remote places that have filled with water due to incorrect fitting of shaft seals just before an Ocean crossing. One had so much water in the engine it never turned over, the other leaked sea water past the pistons so that the oil over flowed out of the dipstick! Neither lost their head gaskets and were running again that day.

 

[Ships_Cat]

The feed must be above the water line and in the antisiphon section. If it is below the waterline on either of the sides then there will be a direct line from the sea to either the engine water pump or the exhaust system. Either way it is unsafe. The best position is the engine pump side and above the water line at all times.

Or more easily, just put an antisiphon loop in the feed line from the engine to the seal.

John

 

[Guest]

I have just read the manual for your particular seal. That is a perfect example of a terrible set of instructions that led to those problems I described.

At no time does it consider that the engine exhaust is below the water line as is common on yachts.

As for the requirement for two engines that is assuming a power boat. It is not relevant to yachts.

Picking the feed from just after the water pump means that if the seals on the pump go the boat sinks even though the boat is left with the sea cock shut.

As for no cooling it is a nitrile lip seal and the web page insists on cooling water.

Depending on your height of the antisiphon either add it above the water or try Vics idea of adding another antisiphon.

I prefer the valveless antisiphons with vents. A small flow of water through the vent ensures that it stays clear and I know if the sea water flow has stopped. Having 2 antisiphons in a system, and depending on hose sizes and heights of the vents, one of them would have no flow.