Raytheon ST-60 instruments
The design of the ST-60 is somewaht different in how they seal the units. While the ST50 depended on snap-fits to keep the water out, the ST 60s are hermetically sealed but have a gore-tex patch to allow the unit to breathe without allowing water in.
Our ST50s are installed on a 45 degree incline, a condition I am sure will aggrevate any problems. Another Prout Escale owner got so discouraged that he put a perspex cover over the ST50s to keep rainfall from hitting them.
Ours cloud over and were repaired a number of times at Ray Marine in New Hampshire. The first time we replaced the displays was not because of condensation - the digits dissappreared when the back light was turned on! Not something you want to discover while pulling into a new anchorage at night. Each display cost us $50 plus labor (ouch!)
I actually considered ripping all the Autohelm stuff out as I consider the Raymarine warranty to be a joke. But the costs and hassles of replacing everything will probably incline me to replace the ST50 display units over time.