I have a 2 year old Astro 1050 (Tracker Marine boat company). It has
a built in-dash depth finder and a Mercruiser 4.3L inboard/outboard.
The depth finder has got the point where it measures fine then goes to
1.1 feet. I constantly switches back and forth. I think it might be
because the sensor is covered with grime since we left the boat in the
water for about 3 weeks. I have cleand the board but cannot find the
sensor for the depth finder. I have looked the engine over and cannot
find it. The speedometer is not affected. I have noticed that when
the motor is trimmed all way up the gauge depth doesn't goes to 0.
So, I figure the sensor is actually on the motor somewhere. Any ideas
where I can find this sensor and what might be wrong if it isn't
grime?

Thanks,
Joe