Radice seal and Vetus syphon loop

[Overandunder]

I've just replaced a Volvo shaft seal with the Radice type which has a greasing point and vent pipe take off moulded in.

Also installed is a Vetus syphon block mounted between the heat exchanger and exhaust elbow (Yanmar 3YM20). This is fitted high in the engine compartment (which equates to about 150-200mm above sea level in my case). The Vetus is the common type fitted with a spring loaded valve, on top of which is a spigot to take a length of narrow bore hose down to the bilge.

I'm aware the Radice doesn't require a forced water connection to the vent when fitted on a sail boat - however to have a constant flow of water over its cutless surface when motoring makes sense to me. So has anyone removed the valve from the Vetus to create that flow of water ? Would the syphon hose then require a T piece to allow air in ?

Any potential issue with doing this ? Of course it will somewhat reduce the volume of water ejected into the exhaust elbow - but is that significant ? The engine has a syphon break fitted in the bilge as well as a high loop before it exits on the starboard side. Appreciate any thoughts.

 

[rotrax]

It has a constant water supply as it is submersed when in the water. If the shaft is locked - ie, in gear when sailing - no water lube/cooling required. If the shaft is rotating, plenty of water already there. Pressure is not needed. I have had two Volvo type seals, both were still as new after eight years service.

Unless the rear cutless is a plain bearing which might significantly reduce water ingress to the Radiche seal, no feed is needed IMHO.

 

[Overandunder]

The othwe aspect is that might simplify

It has a constant water supply as it is submersed when in the water. If the shaft is locked - ie, in gear when sailing - no water lube/cooling required. If the shaft is rotating, plenty of water already there. Pressure is not needed. I have had two Volvo type seals, both were still as new after eight years service.

Unless the rear cutless is a plain bearing which might significantly reduce water ingress to the Radiche seal, no feed is needed IMHO.

The Radiche has a groved cutless profile, which the vent pipe is moulded into. Thinking this over I presume the vent allows rise and fall of the water level due to movement of the boat - so it ends up 'self flushing' anyway.

 

[Kwik Decision]

I'm aware the Radice doesn't require a forced water connection to the vent when fitted on a sail boat - however to have a constant flow of water over its cutless surface when motoring makes sense to me. So has anyone removed the valve from the Vetus to create that flow of water ? Would the syphon hose then require a T piece to allow air in ?

Any potential issue with doing this ? Of course it will somewhat reduce the volume of water ejected into the exhaust elbow - but is that significant ? The engine has a syphon break fitted in the bilge as well as a high loop before it exits on the starboard side. Appreciate any thoughts.

Firstly, yes, you can remove the valve from the syphon breaker to get a continuous flow of water when the engine is running (it is a small flow, so still plenty left to quench the exhaust). However this must discharge into air, not under water, in order for the syphon break to continue to function. I've seen boats with this arrangement, with the discharge just below the toe rail acting as a tell tail, so you can see there's cooling water flowing. If you want to push water through the stern gland you will need a dedicated T in the cooling water discharge, before the syphon break, to supply it, although as rotrax says, this isn't necessary on a sailing boat.

Final point, if you use the syphon break with the sprung valve, rather than a tell tail, itis good practice to take the valve apart once a year, to clean it (or replace it if perished) and make sure it will still open if required.

 

[Tranona]

Really would not bother with the forced water flow. Just take the vent up well above the waterline.

 

[Overandunder]

Firstly, yes, you can remove the valve from the syphon breaker to get a continuous flow of water when the engine is running (it is a small flow, so still plenty left to quench the exhaust). However this must discharge into air, not under water, in order for the syphon break to continue to function. I've seen boats with this arrangement, with the discharge just below the toe rail acting as a tell tail, so you can see there's cooling water flowing. If you want to push water through the stern gland you will need a dedicated T in the cooling water discharge, before the syphon break, to supply it, although as rotrax says, this isn't necessary on a sailing boat.

Final point, if you use the syphon break with the sprung valve, rather than a tell tail, itis good practice to take the valve apart once a year, to clean it (or replace it if perished) and make sure it will still open if required.

Thanks - good point about the pressure. Probably not worth the trouble and will leave as is !

 

[rotrax]

The othwe aspect is that might simplify

The Radiche has a groved cutless profile, which the vent pipe is moulded into. Thinking this over I presume the vent allows rise and fall of the water level due to movement of the boat - so it ends up 'self flushing' anyway.

Yes, my current boat has one. The bearing BEHIND the Radiche seal would restrict water supply to the seal were it a close fitting plain bearing. If it is a normal grooved cutless, it will be fine. Clip the vent pipe up well above the waterline and all will be well. The vent pipe is fitted so there is no need to 'burp' the seal to displace air after drying out. No other reason.