Why is this plus cable from the house battery bank connected to the engine (VP MD2040

[jonase]

I have a Volvo Penta MD2040-D from 2004. Trying to figure out why I have an additional plus (+) cable connected to the engine from the house battery bank.

- The plus (+) on the start engine is connected to the start battery.
- The plus (+) from the alternator is connected to a VP Battery Isolator to share the charging from the alternator to the start and house batteries.
- The minus (-) on the engine is connected to a shared minus plint for both the start and house battery bank.

But there is also another plus (+) cable from the house battery bank that is connected to the fuel pre-filter and then connected to the engine underneath the oil filter.

Can someone please help me understand why is the engine connected to the house battery bank?

Where the cable is connected to the engine
https://imgur.com/a/FYc4JP3

Photos of the cable connected to the fule filter and the engine
https://imgur.com/a/Pzv1srQ

[Tornadosailing]

I'm assuming you believe this to be a positive cable based on the wire color. It appears to simply be a bonding cable to make sure everything remains at the same ground potential. This limits galvanic corrosion. The electricity doesn't care what color the insulation is, but the installer didn't do you any favors by adding to confusion.

[jonase]

Originally Posted by Tornadosailing

I'm assuming you believe this to be a positive cable based on the wire color. It appears to simply be a bonding cable to make sure everything remains at the same ground potential. This limits galvanic corrosion. The electricity doesn't care what color the insulation is, but the installer didn't do you any favors by adding to confusion.

Unfortunately it is connected to the positive on the house/equipment batteries. I just did a documentation and labeling of the battery banks and found this odd cable.

It's hard to see on the photo but it is connected to the positive of the house battery bank.

Starting to think that maybe you are right but it has been incorrectly reconnected due to the color. Boat is new to me so don't know how long this has been wrong if it is a bonding cable...

https://imgur.com/a/Qmo4iQo

https://imgur.com/a/gSOrL9y

[Tornadosailing]

Then my question would be where is the fire? Connecting a positive lead to the engine block would result in an immediate burning of the wire in question. Unless of course whoever made the connection didn't make a proper connection to the engine block.

In any case, you need to get someone to look at it who knows what's going on. Positive wire to the engine block is always wrong.

[Tornadosailing]

I took a closer look at your pictures. It looks to me that the wire in question at the fuel filter and engine block are black with a red stripe. I don't see that wire going to your battery. Are you 100% sure it's the same wire?

Also, replace your fuel hoses before you have to start fighting an engine dying issue.

[Cheechako]

That wire is grounded. If it was going to your pos battery post you would be burning. Recheck the wire identification.

[jonase]

Thanks for the comments, I will recheck tomorrow.

I will also definitely replace the fuel hoses this winter! Thanks for pointing this out.

[Brewgyver]

Also, though it’s hard to be definite from a photo, they don’t look like the same gauge wires.

[Squanderbucks]

These are ground wires to the filter block. Because the filter was moved to an off engine mounting it was necessary to re-ground it. But instead of using a good grade of marine wire of adequate gauge the installer used some cheap speaker wire and left you scratching your head.
Replace it with something like a piece of Black marine wire possibly 10 Ga or so - no need to use two wires - just one of the proper size.

[jmschmidt]

Typical of this forum. People answering questions you didn't ask. I don't believe you said anything about this extra red wire going from the "house batteries to the engine block." Rather you said. "Trying to figure out why I have an additional plus (+) cable connected to the engine from the house battery bank." I took that to mean to the engine starter lug, which should be red, and not to the engine block. If this is what you meant it would mean that all batteries are connected to start the engine, not just the start battery. This function is usually accomplished with a battery switch (Blue Sea makes one) that can perform this function to gang all batteries together if the start batter is too low.

[DougR]

He didn't state that the wire is connected to the engine BLOCK, but he did state that the wire is connected to the engine beneath the oil filter, and he supplied photos, complete with arrows, that clearly show the wire connected to the engine flywheel housing, not the starter motor. The starter motor is on the other side of the engine.

For my money you can take this wire off of the primary fuel filter and dispose of it. There is no ABYC or ISO requirement that I am aware of which requires a ground wire to a remotely mounted primary filter housing. I don't think there are any galvanic issues here.

DougR

[Tornadosailing]

Originally Posted by jmschmidt

Typical of this forum. People answering questions you didn't ask. I don't believe you said anything about this extra red wire going from the "house batteries to the engine block." Rather you said. "Trying to figure out why I have an additional plus (+) cable connected to the engine from the house battery bank." I took that to mean to the engine starter lug, which should be red, and not to the engine block. If this is what you meant it would mean that all batteries are connected to start the engine, not just the start battery. This function is usually accomplished with a battery switch (Blue Sea makes one) that can perform this function to gang all batteries together if the start batter is too low.

A cursory glance at the photos would show you that the wire in question is bolted to the ENGINE BLOCK. If you took that to mean the engine starter lug, that's on you.

[zboss]

Originally Posted by Squanderbucks

These are ground wires to the filter block. Because the filter was moved to an off engine mounting it was necessary to re-ground it. But instead of using a good grade of marine wire of adequate gauge the installer used some cheap speaker wire and left you scratching your head.

Replace it with something like a piece of Black marine wire possibly 10 Ga or so - no need to use two wires - just one of the proper size.

If it were a ground it would be attached to the ground buss, not the positive post.

[Tornadosailing]

Originally Posted by zboss

If it were a ground it would be attached to the ground buss, not the positive post.

I can assure you it's not attached to the positive post, as evidenced by the lack of fire. He has simply mistaken which wire is which when chasing them from the engine to the battery.

[hzcruiser]

Originally Posted by Tornadosailing

A cursory glance at the photos would show you that the wire in question is bolted to the ENGINE BLOCK. If you took that to mean the engine starter lug, that's on you.

Oh well, he also suggested that this flimsy wire is used to "gang the batteries together" to support the "starter batter"...