Turns out I have an Standard Horizon AS45, and it has the same plug and sleeve arrangement you describe. So now I can swap the plug out without pulling and bedding the sleeve. That’s the part that I was dreading. But if it’s the unit itself that gets cooked and not the speed sensor in the water, you could just disconnect it at the unit.......and save swapping the plug for serious road trips....like CBR’s, and such.

I have all the instructions for both this unit and the depthfinder half of my Garmin GPS/depthfinder and they are just as you described them.

The unit’s I was talking about are more like Eagle/Lowrance/Hummingbird type depthsounders, with speed sensor. The transducer and speed sensor are all one unit. They are not through hulls. These are almost impossible to mount anywhere but on the transom.

But I learned something new today, and can now go to bed!

Howard