Low voltage ???

New group 31 agm battery.........Im getting low voltage on bow depth finder ( 10.4 / 10.5 volts )....also low voltage on console unit. Battery is 800 cca / 1080 mca and checks good . With engine running , the voltage goes up to 13 + volts. Is it likely that the inline circuit breaker on the accessory wire is a possible culprit here ? BTW , All connections on the block on the transom look clean and are tight . Any insight on this problem is welcome.ThanksDon