Dan Best wrote:

I used to have an analog SR Mariner of the same vintage that would
sometimes read exactly double the actual depth (confirmed with a lead
line). I wound up replacing it with a fish finder, even though it
wouldn't go into the same hole (I covered the hole with a nice looking
teak piece, then eventually mounted something else into the teak
piece). After having used the fish finders on two boats now, I would
never go back to a simple depth finder. Instead of showing me what the
depth is at this instant, it now shows me whether its rapidly shoaling,
rocky, smooth, etc..

Good luck - Dan

Ryk wrote:

just last week it was reading a solid 30 feet in water that was
demonstrably about 10 to 12 feet deep based on visually confirming
vertical anchor contact with bottom. The bottom was weed-free hard,
flat mud/clay. Later on it was reading less than my draft in an area
where I knew I had at least ten feet to the top of the weeds.

I know that the obvious answer is "get a new depth sounder" but
thought I might ask if anybody knows of any miracle cures.



Reducing gain in older models can reduce multiple echos which can
come at just over one rotation of the scan blinker, showing
perhaps 1 foot where the water is 51 feet deep, while using the
50' range, etc. Bubbles, fish and keel echos can also present
mysteries akin.

A little lube on the rotating shaft can clear some things up, and
the delicate shaft end contactor must be kept clean. The rpm is
limited electronically, except where bearings are gummy. They
seldom overspeed causing false deeper indicator errors, but when
they do, the servo is easily fixed, it is almost always a
regulator chip. I had, and fixed, a few. A slow rpm shows false
shallow indications. The bearings on these older systems can
become uncooperative intermittently depanding on temperature,
humidity, dust, and smoking gum accumulations.

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