Back in the early 1960's, Columbian Bronze Corp. was exclusively a propeller manufacturer, manufacturing sand cast and machined propellers for small and large craft, ranging from several inches in diameter for small outboard motors up to giant propellers up into the 20'-30' diameter range. Columbian realized they could sell marine electronics equipment through the same distribution network as their small outboard and inboard recreational boat propeller lines, and they contracted several electronics design/manufacturing firms to make marine electronics products for them private branded. These products included the Aqua Guide RDF, Aqua Comm AM marine radiotelephones, Aqua Probe depth finders, and Scentry gas vapor detectors, plus some lesser accessory items such as rudder angle indicators, some engine instrumentation, etc. The Aqua Comm transceivers were tube-type units, but around that time (late mid-to-late 60's) transistor products were taking over the electronics industry and most of the rest of the Columbian Hydrosonics line were transistorized products. In the late 1960's Columbian started manufacturing some marine electronics products in-house… most notably the Aqua Probe and Scentry lines… the others remaining private branded. In the early 70's a new model of Aqua Guide was designed and manufactured in Japan. As time passed Columbian found that their small recreational boat propeller lines were being outsold by the outboard motor manufacturers who were marketing die cast aluminum propellers in different diameters and pitches for custom applications much less expensively than the sand cast and machined props manufactured by Columbian. As a result, Columbian found the need to address two different marketing and distribution programs, one for recreational boating (marine electronics) and a second for commercial (BIG!) propellers. It is very hard (impossible?) to move a foundry, but much easier to sell off an electronics division… thus the sale of Columbian Hydrosonics to Aqua Meter of Roseland, NJ in August of 1975. This information was provided by former Columbian Hydrosonics Chief Engineer Henry G. Grilk.