Depth sounder that does not need a hole drilled in boat?

[pvb]

Not wishing to be negative but I think it is important to point out that an internally-mounted transducer loses a certain amount of gain by dint of having to transmit through the hull. While this doesn't affect accuracy it can have an effect on the overall range of the sounder, resulting in no readings in deeper water. To most sailing people this is immaterial but to those looking to find fish in deep water it is something to be borne in mind.

Of course the huge plus is one less hole in the bottom of the boat, something which isn't to be sniffed at!

I'd agree - a through-hull transducer will always be superior. But I disagree with your comment about a hole in the boat; it isn't a hole, it's filled in with a transducer and completely sealed. At the sort of depth in a typical boat, there's virtually no water pressure on the "hole". Those of us who've had to remove an old transducer will testify to the fact that they're pretty well fixed!

 

[fisherman]

Didn't know that about castor oïl. But difficult to buy because it might be used for 'medical' reasons? Bit nanny state...
Mostly smelt in exhaust gas on race tracks, as very stable at high temps.

...Castrol 'R'..?

 

[DownWest]

...Castrol 'R'..?

That's the stuff. Without looking, I understood castor was mixed in with other oïl, as even a small % worked.

 

[fisherman]

My Koden CVS 128 fires through the hull with a 1kw tranny. Checked it out today, I could see the 4 oz lead and the plastic lure next to it in 100 ft of water, it wasn't turned up full. It easily shows the individual tiny crabs that I've chucked.

 

[Iminei]

Just sent PM Steve, but your inbox is full. I have some Nasa depth kit going spare if it is of use.

 

[QBhoy]

I have a skin fitting transducer for the Garmin 550s. Didn't need to drill hole. Just sat in bilge with a blob of silicone and manages through hull. Worked on a fairly hefty built 1989 Sealine and most recently Kevlar re enforced campion hull.