I'm in process of re-rigging wiring and engine compartment on my 1987 SR357. I have Factory Wiring Diagrams and they don't show anything about a BONDING system.

I'm getting confused by BONDING system and GROUNDING System.

Are they connected to same point in system finally or are they two (2) seperate and isolated end-points?

Best I can tell there should be a GREEN wire connecting all thru-hull, water fittings and to Outdrive Bonding system AND there should be a BLACK ground wire connecting all the 12 volt stuff that ends up at battery NEGATIVE terminal.

Where does the BONDING--GREEN wired get terminated--???

I also posted in Technical Section--

I think that you want them all to go to good ground. If they all go to a good ground they all have the same potential and you are ok. Grounding to the same location is the ideal but not required as long as the groundsa are good. Bonding vs. Grounding is more or less the same thing. They use the term bonding as no electricity really flows through your trim tabs but they should be bonded/grounded to avoind corrosion.

Jon

Bonding is the process where you tie all the metal underwater fittings together and then attach a sacrificial zinc to the entire bond. This is the purpose of the big zinc plate you will see on the back of lots of yachts. Any stray current in the water will eat away the zinc and not your through hulls, drive, whatever. BUT-if the zinc goes away then the next lower grade metal starts to go away-on your boat that is the outdrives If the boat is not kept in the water very much bonding is not necessary but if it is bonded you need to keep up on the zinc. Also a bond system should not be grounded to your 12V ground.

Should I add one of those zinc plates to transom while I've got engines out?

Inspect good point about the seperate grounds. I just re read my post from this am and I did not make that clear. When I said grounds to the same location I meant electrical grounds not the bond....

Jon

If the boat is going to spend a lot of time in the water it might be a good idea, but if it is lifted or trailered it is just added weight and expense.

Talked to Formula Tech Support and got following--

Formula started putting Bonding Systems on boats in late 97 or after.

They used scheme as follows--

1> 8 guage wire -- light green, preferrable home runs on each side from each point to central Bonding plate;

2> Points attached via thru hole bolts--lifting ring, Inner Transom Plate, Transom Water Pickup, Drain Plug, K-Plane; Seacocks (genset and a/c)

3> Optional--Sea water strainer(s), oil cooler(s)

4> Terminate wire with ring and star washer;

5> run to a large grounding bus and connect that bus to negative battery post

I'm gonna head out and get a bunch of wire and terminals and make up a new "rat's nest" for tonites project and start stringing tomorrow...

FWIW--

Poorsche