Oil for depth sensor

[Swifty]

Have installed a Garmin through hull depth sensor. A well is bonded to the inside of the hull and filled with oil, sensor is then immersed in the oil and sealed. Garmin specify a mineral oil. Any recommendations for which mineral oil?

Tim.

[Pipster100]

Hi Tim,
Castor oil will work ok, basically you're looking for an oil with a similar density as seawater, the idea that you wan't the sonar pulse to travel through the oil at around 1500m/s (same average as seawater) so you minimise errors.

Instead of making a well that you sit the transducer in and fill with oil, the other option is to just Sikaflex the transducer straight onto the hull. I've gone this route on my RIB. Works well too.

If you decide on the Sikaflex route, then make sure you get a complete seal with no air bubbles under the transducer or you will find it doesn't give an accurate depth if at all.

[Ribtecer]

^^^ Wot he said, worked a treat and I've tried it that way on two boats. 👍👍👍

[Pikey Dave]

My Airmar M260 uses Glycol antifreeze as the media. Cheaper & less messy than oil.

[Matt]

Instructions for my GT15M-IH says oil or antifreeze