Things that almost work: water speed transducers

Does your BCC have a water speed transducer of the sort that comes with a bung that plugs the thru-hull when you’re not sailing? I have a Raymarine ST60 water
speed system of that type.

My problem, big enough to make me put the ST60 water speed system in the category of ‘Things that work, imperfectly’ is handling the ingress of water when I change the bung for the transducer or vice versa.

Don’t get me wrong: I enjoy the ST60 water speed system on Zygote. Combined with her Raytheon ST60 wind system, it gives me true wind. And combined with her
Raytheon Raychart and GPS, it calculates and shows tidal stream vectors.

Has anyone worked out a way to minimise the in rush of water when changing bung for transducer? The flapper valve in the thru-hull reduces the flow, but is a
joke. Zygote’s thru-hull is near the foot of the mast, so after every change I flush the area with freshwater, wax the mast, and spray nearby electrical
connections with silicone.

I’d be grateful on tips and tricks dealing with the water speed transducer. In return, I’ve attached a file (, about 80K), with the HTML
version of the section on bilge pumping in my growing-but-not-finished Operating Manual for Zygote.


BCC28 #116 Zygote