Lube Type for Speed Transducer?

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Mark Sutherland

I've noticed a lubricant of some sort on my Raymarine speed transducer unit when I pull it out of the through-hull sleeve to clean it.   Does anyone know, or can recommend the type of lube to use for this purpose?  I'm guessing it might be the same lube as what is used for through-hull valves?  Thanks.
Dunrobin II, 1986 C34 MK1 #170


If you're referring to the O rings then good old petroleum jelly works great.
Ciao tutti



Better than Petroleum Jelly, is Super Lube.  Petroleum based products are not good for rubber.

Roc - "Sea Life" 2000 MKII #1477.  Annapolis, MD

Ron Hill

Mark : The lube that you noticed is probably silicon based.

A thought
Ron, Apache #788


Simple rule - but not so simple in real life:
Ideally lube all rubber o-rings EXCEPT silicone ones with silicone grease and use non-silicone grease on silicone o-rings. In other words, use a grease that's the opposite of the o-ring material.

In practice it is hard to always know what a given o-rign is made of, but fortunately using a thin layer of even the wrong grease rarely causes serious problems.

The issue is that greases formulated from the same base as the o-ring (or from an incompatible base) tend to swell or even degrade the o-ring. This is well documented by the o-ring manufacturers, but not always prominently.  I have dealt with it in scientific and industrial applications and verified it with the manufacturers.  Materials such as Nitrile, Buna-n, EPDM, Viton all show excellent compatibility with silicone-based greases. Silicon rubber, on the other hand, tends to swell and/or get sticky after extended contact with silicone oil.

In practice, though, I have not seen any serious issues with using Super Lube Synthetic Grease on various rubber and silicon o-rings. I have also gotten away with just vaseline in non-critical applications, which would include the o-rings on the speed sensor. Remember to lube the ring at the top if there is one, as in my case that was the one that was responsible for it being hard to insert.