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I am refitting my boat with Raymarine gear; a78 MFD, CP200 sidevision sonar, and an EV100 autopilot system.

I have a question concerning the termination of the drain wire. My boat does not appear to have a common grounding point. I see in the manuals that it is permissible to wire the RF drain wire directly to the negative of the battery.

I have installed a new fuse block specifically for the new electronics. It is ran back to an independent battery that will be used only for the new electronics. Engine start and all pre existing electrical components are run off a separate battery (although I plan to set it up so the engine will charge the new battery when running).

That said, can I just terminate the RF grounds with the negative wires from each individual power cord for each individual component together at the newly installed fuse block?

It is not recommended that you do as you have suggested. Please click here to view a FAQ addressing this subject.
OK. Do you have a recommended gauge of wire to connect the drain wires back to the engine block? The run will be 15 - 20 ft tops.
Raymarine has not specified a recommended wire gauge for extending drain leads. I used 14 gauge for similar length drain extensions onboard my own boat.
OK, thanks for this information, much appreciated.
You're welcome.

I have a bonding cable and an inboard but getting the drain wire to them would be difficult. Can I just got to the negative post on the battery?


As challenging as it may be, it is recommended that the drain leads be routed to the bonding cable per the FAQ referenced within my initial response to this thread.
Just out of curiosity, what does the RF drain wire actually do?

This is the first time I've come across this, none of the other marine electronics I've installed in the past from other manufacturers had this wire.

It is possible that less well designed / lower cost marine electronics may not have manufactured to support bonding. Bonding is recommended by NMEA in its Installation Standards for Marine Electronic Equipment Used on Moderate-Sized Vessels. Electrical bonding and RF drains are intended to prevent static electricity build-up that can interfere with radio and navigational equipment. Proper bonding will also assist in prevention of galvanic corrosion and with lightning protection by allowing the current to pass through the vessel's structure with minimum arcing. Finally, bonding prevents dangerous static discharges in fuel tanks and hoses.
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