Ultrasonic Metal Thickness Meter

Colleges
while in the middle of hull repair I thought about all the places the I may have missed finding corrosion holes in the aluminium plate. I had this strange thought about using an ultrasonic stud finder and running it all over the hull to find thickness variations in the metal, then I realised I would be working in reverse.
A quick google and search and I found one of these metal thickness detectors, especially made for the purpose.
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=230561769896
Has anyone used one or have experience with one? while the vessel is in the welding position $140.00 is cheap insurance if I locates another spot to be repaired.
I am open to thoughts and suggestions.
Please the option of removing the deck to gain access to the hull is not an option.

 

Ultrasonic micrometers are fairly common. A good one will run close to a thousand dollars, but it is an indispensible tool where the application exists. I use one of them for measuring thickness variations in engine blocks and cylinder heads. More serious uses include oil pipelines, water tanks, boilers, and vessels of many descriptions.

The measuring head, the probe that is placed against the mettalic part, is material specific. Aluminum may need a different head than one that is calibrated for cast iron or some other material. I'd be suspicious of the $140 model that you mention.

 

I can see your point about $140.00, I was just going by what the add said, says it does steel Aluminium , PVC ect. In my application I dont think I need that 0.1mm accuracy, All I really need to know is if its 5mm pate and suddenly I find a 3-4mm section I know that it needs to be cut out. But then how long will it take me to run over both bottom plates of a 20' boat? Or is there a better way?