[CA] CP370, TM258

[Doublecabin]

Have recently installed a TM258 (3months ago) and replaced a DSM 300 with a CP 370 (6 weeks ago) running on a e140W.
Everything has been running good (Numerous trips)before yesterday. Yesterday loss bottom and scrolling at 65'. Kept running out 45 minutes or so and fished all day (anchored) at approx 100' with no accurate bottom. When anchored machine showed bottom occasionally at 0-30' when we were actually in 100'+. There was no scrolling of bottom, however just a bunch of what I would call interference. Re booted cp 370, e140w and entire system to no avail. Also checked tm258 for obstruction or movement and there was none. Stayed out in 100' for 5 hours with no sonar. On way back in at 65' (again) unit started working.
Someone at marina said this is not uncommon for ray and there is a fix?? I searched the forum and did not come up with anything specific.
Any suggestions to resolve this would be appreciated.

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum Doublecabin,

The symptoms which you have identified may well occur when the flow of water passing beneath the face of a fishfinder transducer becomes aerated such as can often occur when a vessel operates at planing speeds. Of the three transducer mounting styles (Thru-hull, In-hull, and Transom-mounted), the transom mounted transducers are typically most susceptible to aeration at planing speeds. Please click here to view a FAQ addressing this subject. Should aeration cause the fishfinder to loose bottom, then the sounder will hunt in an attempt to reacquire bottom. Should the sounder not reacquire bottom shortly after the vessel has stop or is operating at trolling speeds, then it would be recommended that the operator abandon automatic depth ranging and then manually configure the depth range to be one range increment deeper than the charted depth (examine the spot soundings and/or depth contours within the Chart application) at the vessel's location. Once the sounder has reacquired bottom, then the sounder may once again be configured to automatic depth ranging.