Thru hull fittings below the boot stripe

[Ferg]

Ok, So. I have an ST40 Raymarine bidata that I plan to install in my sweet ol’ mid 70's C27. I’m having some trouble giving details as she’s buried in several feet of snow. In fact, a 200 ton icebreaker is stuck out in the bay right now. Anyhow, for speed and depth sensors, does anybody know if the hole size is standard sized? I have an older bidata that works OK but would like to know if:1. Can I use the old sensors?2. Is the hole for the sensors a standard?3. What’s best for sealing the opening where the sensor goes?I will update and refine my questions as the snow melts and I can get to Sea-Renity. So if you have knowledge or experience, please check this post from time to time. Fate favours thems who is prepared, eh? I hate sinking as much as making new holes below the boot stripe…..

 

[Rick]

No standard size that I'm aware of

I've seen 1 5/8" -- 1 3/4" & 2". I have a 93 catalina that had standard horizon instruments. I'm in the process of replacing them with a ST40 bidata and the thru-hulls that came with the unit are 2" as were the original ones I removed. In my research I found that most of the transducers out there are made by AIRMAR. Both Navman & standard horizon told me you can't just use any transducer you have to buy it from us because its matched to the instrument. Well thats almost true, if you know thw specs you should be able to match the instrument to the transducer or the transducer to the instrument. Go to their web site and use the product search and you will probably find what you need. My ST40 came with a P19 & ST300