Deep Sea Seal - water injection

[JimC]

My boat, which I bought second hand a year ago, is fitted with a deep sea seal. The water injection isn't into the seal itself but into the sterntube about 6 inches behind the seal. It takes a lot of the cooling water, at least as much as goes into the exhaust injector and I'm getting some steaming of the exhaust which I think is caused by this.

I'd like to blank off the water injection pipe in the sterntube and instead inject a much smaller volume directly into the seal itself, which has a Y adaptor fitted. Can anyone give me any advice about this, e.g. what do I use the other branch of the Y for, is it for a vent? does it have to be brought up above the waterline?

 

[penultimate]

Yes, the other branch from the Y is a vent and if you don't bring it above the waterline you'll be surprised how much water it will deliver!
I take the cooling supply from between the seacock and the engine raw water pump inlet; and I lock the shaft in gear when sailing.

 

[PaulJ]

I understood that whether or not injection is needed depends on the speed of the boat. The tube should be full of water which enters through the cutless bearing and most sailing boats do not go fast enough to empty the tube and so should not need injection.

I have a PSS seal (but STILL have not launched yet - should be May/June now). The PSS is similar to the Deep Sea and I was not intending to use injection.... what do others think?

PaulJ

 

[30boat]

I have fitted three deep sea seals over the years to my boats and have never bothered with water injection.As posted before the speed a sailboat travels at is too low to empty the sterntube.
N.

 

[Strathglass]

Don't know what kind of craft you have so it is impossible to guess which deep sea seal you have.
If we assume you have a yacht as you have posted on this forum , not the mobo forum, then your engine will be an auxillary.
If this is the case the vent on the seal is only there to release any air trapped in the seal when initially launching. Once this is done there is no requirement for venting.
Any trapped air can also be released by squeezing the bellows after launching.
It is quite easy to fit self venting by various methods. I have arranged mine to be vented by fitting a Y piece on the outlet from the vent tube of the Vetus inverted U bend which is fitted between the engine water output and the water injection pipe to the exhaust system.

I have also used dry venting with a small pipes led well above the waterline on a twin engined cruiser.

Remember that any venting is another potentiol source for the unwanted entry of water.

Iain


Don't know if this will help.

 

[Landale]

I've a PSS seal and the instructions IIRC say water injection is not needed below about 17kts.

What they don't tell you, and seems to happen with me is that you can get a gas build up in the bellows of the seal - dead shrimps fermenting etc etc so bleeding every so often, particularly if unused for say a month is a good idea.

Apart from that much happier with this kind of seal that the stuffing box type stern gland.

Landale

 

[john_morris_uk]

I was interested to hear about your build up of gases in the PSS seal bellows. We have had two of these and have never experienced any gas build up.

Like others, we have been very happy with the PSS seal. Reasonably priced (about £100 I think) and no need to water inject.

It was Andy in Yachtparts that put me on to the PSS seals.

 

[kandoma]

I have a PSS seal since 7 years and no injection. Forward no problem, backwards big problems. Manovering is ok, but I can not run the engine in idle and propeller engaged backwards for several minutes (for troubleshooting the gearbox). The carbonring started to melt.

Peter