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The temp on my fishfinder was off 20 degrees this weekend. it seemed to be accurate if you added 20 degrees to the readings. have never had issues in the past. actual temps were 67 inshore up to 76 in bluewater as verified by others. mine were within 1 - 2 degrees if you added the 20 so when i got to the warm water mine was reading 56. its a raymarine dsm 300 with a b260 transducer. there is a +/- 10 degree calibration setting but only 10 (not 20) and it was set to zero. anyone have any experience with anything like this? i guess i will try to call ray customer support next. Thanks, Bill

Bill,
Check the transducer for barnicles over the temp sender dot on the flat surface, also check your ground wire connections, spray the plug connections at the back of the unit and look for a bent pin on the male end at depth display.
Pete