There has been a lot of discussion of this recently.

The Marinette engine is grounded to the hull. Mine were grounded to a stud thru a floor beam at the front of the engine compartment, and the batteries went to the same stud.

This is OK because the engines are electrically isolated from the shaft and prop, which must not touch the hull.

My trim tab pump and head, as well as a few other things, were also grounded to the hull. This is bad, there should only be one point of contact between power returns and the hull. You can't make a reliable connection between copper and aluminum, anyway.

It is best to have few connections and shorter wires in the starting circuit, and to accomplish that you can wire with heavy wire directly from the battery negative to a stud on the starter, and then take a smaller wire from the same stud to the boat's ground. This is the way most trucks and cars are wired - the battery negative goes to the block directly, and then to the frame.

If you have two engines and two batteries, and can start either engine from either battery using switches, then you will need to either put heavy wire between the two battery negatives, or connect battery negatives and starter negatives all to one stud. This is so the starting current can get back to the correct battery.

There is a pdf on my website (32' Marinette Wiring) that shows how I did it, perhaps it will be useful. I have diesels, but they start the same. There is also some 'generic' wiring that is all I know about what the factory did, under Marinette Wiring, Generic. www.geocities.com/dougmrose/

Before you go back in the water, make sure you have no connection between hull and shaft. When I got my first Marinette, someone had assembled the flange insulator improperly and there were bolts from the shaft flange thru the transmission flange.

No.

Jeff

The resistor idea is a good one for preventative maintenance checks. I purchased my 'M' this spring and before I splashed I had to go over the electrical system which resulted in snipping and clipping nearly a bushel basket full wiring that went nowhere. It was surprising that there hadn't been an electrical fire at some point.

I'm pulling the engines and will strip all wiring. I want to install a breaker panel, rerun all AC/DC wiring and build in some diagnostic/monitoring capabilities, should be fun. Have you considered or do you use mutilcore cabling? At the minimum I plan on running all wiring through conduit.

Not only use multi-strand wire, but use Ancor marine wire - the strands are tinned to prevent corrosion.

It is much easier to wire with 2-wire cable, red for power and yellow for return. The proper return path sort of takes care of itself.

You might consider getting http://skycraftsurplus.c...IEWPROD&ProdID=1542 which is 14-ga marine (tinned) wire for about $50/100', a good price. I use wire from these guys all the time.

Be sure to use stranded, tinned, 3-wire cable for AC, so you can carry the green ground as well as the neutral. 14 AWG is the right size.

I have posted the way I have handled the power wiring on my boat, it is at www.geocities.com/dougmrose select '32 Marinette Wiring' to get the schematics in .pdf form. The diagram of the power wiring is Sheet 6.

This is all from scratch: I removed miles of old zip cord, odd bits of automotive wire, and weird rusty things that didn't seem to be connected.

I mounted five breakers on the top of the kickpanel under the wheel, so that they would be easy to reach. I ran a 10 gauge two-wire cable from each to the system to be powered. Note that I powered the Accessory Panel (eyebrow) in two halves: Port half has mostly lights, starboard half has mostly pumps and electronics. The Accessory Panel grounds are also in two halves.

It is important that any load wired to a portside switch have its return back to the portside power, and so on. If the grounds get interchanged, or a ground is 'borrowed' from something near by, troubleshooting will be a nightmare.

Note that "trim tabs" are powered by a switch on the port side of the accessory panel. I ran new 10 ga cable from the panel down the tube and all the way back to the hydraulic pump near the transom. This lets me power the pump through the panel switch, and brings the return back to the panel. See sheet 14. Power to the various trim tab switches all comes from the pump, which I have not shown.

Engine wiring is completely separate from the boat's, and each engine is separate. This way a fault in the boat's circuits can't stop an engine, and a fault in one engine can't stop the other.

Don't know if all this is necessary, but it is the way I was taught.

Stray currents are probably not a big problem in the hull, because the hull is welded and has very low resistance - still it is bad practice to use it as a power return, and a connection to aluminum can't be trusted anyway.

I just tried http://www.geocities.com/DOUGMROSE/ and it seems to work. Yahoo is discontinuing Geocities and so I will have to move the site elsewhere. Not looking forward to it - at my age I just want to figure out better ways to open beer, not all this website stuff. I guess I'll have to find a good html editor and a new place for the site....

Thanks, Doug! You and your team rule.