CCred68046 wrote:
I have seen this grounding questions with metal boats before and I dont
understand what the issue is. If the boat has a motor I can almost guarentee
its grounded somewhere to the hull weather its inboard or outboard. Would
someone actually go through the trouble and expense to isolate the electrical
system from the hull? That would take a lot to do!!

The debate is long & I'll stay out of it for now, however you are
mistaken Cred about "almost guaranteeing" engine electrics are grounded,
indeed most proper marine engine electrics are not.

True marine electrics even on big diesels where the spark risk is
minimal, have all their electrics above ground. The starters &
alternators etc have their own earth returns kept above the cases, so if
the user/engine manufacturer chooses you can have a completely above
ground system with none of the electrics able to get to the prop shaft
etc via the block.

Diodes leak.


K.

I'll stay out of it for now, however you are
mistaken Cred about "almost guaranteeing" engine electrics are grounded,
indeed most proper marine engine electrics are not.


How can they not be? Every DC and AC motor I know of requires a + and -
current to run. I consider the - to be ground. The outdrive is connected to the
engine which must have a + and - (or ground) to run, and is fastened to the
metal hull. If theres no continuity there you will have to show me with a VOM.

True marine electrics even on big diesels where the spark risk is
minimal, have all their electrics above ground.

Define "above ground". Again, they require a positive and negitive to operate.


The starters &
alternators etc have their own earth returns kept above the cases, so if
the user/engine manufacturer chooses you can have a completely above
ground system with none of the electrics able to get to the prop shaft
etc via the block.

And the block is grounded (or negitive) and is connected metal to metal to the
metal outdrive which is bolted to the metal hull. The connection might not be
the best but it is there and I have to believe its making a pretty decent
connection. I have an aluminum boat with an outboard and there is definately
continuity from the hull to the motor.. It would take some pretty serious
custom made isolators to stop it.
I can admit it when I'm wrong so if someone can show me that I am I would like
to know how they work.

"CCred68046" wrote in message
...
I'll stay out of it for now, however you are
mistaken Cred about "almost guaranteeing" engine electrics are grounded,
indeed most proper marine engine electrics are not.


How can they not be? Every DC and AC motor I know of requires a + and -
current to run. I consider the - to be ground. The outdrive is connected
to the
engine which must have a + and - (or ground) to run, and is fastened to
the
metal hull. If theres no continuity there you will have to show me with a
VOM.

True marine electrics even on big diesels where the spark risk is
minimal, have all their electrics above ground.

Define "above ground". Again, they require a positive and negitive to
operate.


The starters &
alternators etc have their own earth returns kept above the cases, so if
the user/engine manufacturer chooses you can have a completely above
ground system with none of the electrics able to get to the prop shaft
etc via the block.

And the block is grounded (or negitive) and is connected metal to metal to
the
metal outdrive which is bolted to the metal hull. The connection might
not be
the best but it is there and I have to believe its making a pretty decent
connection. I have an aluminum boat with an outboard and there is
definately
continuity from the hull to the motor.. It would take some pretty serious
custom made isolators to stop it.
I can admit it when I'm wrong so if someone can show me that I am I would
like
to know how they work.


There is no requirement for the coil(s) to be grounded to the case. While I
have no experience with a floating ground in a 12 or 24 volt ignitions, all
high voltage motors and generators that I have ever worked with are isolated
from the frame. There is no practical reason that a low voltage system
can't be wired the same way.

The only area where it may be difficult to separate the ground from the
frame is the spark plugs. Even this is not an insurmountable problem; it is
possible to make a spark plug with two electrodes. The only place I have
seen this used in practice is turbine APUs.

Mark Browne

K Smith wrote in message ...
CCred68046 wrote:
I have seen this grounding questions with metal boats before and I dont
understand what the issue is. If the boat has a motor I can almost guarentee
its grounded somewhere to the hull weather its inboard or outboard. Would
someone actually go through the trouble and expense to isolate the electrical
system from the hull? That would take a lot to do!!

The debate is long & I'll stay out of it for now, however you are
mistaken Cred about "almost guaranteeing" engine electrics are grounded,
indeed most proper marine engine electrics are not.

How can an electrical circuit be made if there isn't any ground?

"basskisser" wrote in message
m...
K Smith wrote in message
...
CCred68046 wrote:
I have seen this grounding questions with metal boats before and I
dont
understand what the issue is. If the boat has a motor I can almost
guarentee
its grounded somewhere to the hull weather its inboard or outboard.
Would
someone actually go through the trouble and expense to isolate the
electrical
system from the hull? That would take a lot to do!!

The debate is long & I'll stay out of it for now, however you are
mistaken Cred about "almost guaranteeing" engine electrics are grounded,
indeed most proper marine engine electrics are not.

How can an electrical circuit be made if there isn't any ground?

It has one - It just does not use the engine or drive components to provide
the current return path; a separate "ground" wire carries the juice back.
Look up "ground loops" on google. This type of wiring allows effective
assaults on this nasty problem. If you are trying to eliminate radio
interference problems or reduce electrically induced corrosion problems,
this can make a lot of sense.

There have been a few times that I wished that automotive components were
built this way.

Mark Browne

basskisser wrote:
K Smith wrote in message ...

CCred68046 wrote:

I have seen this grounding questions with metal boats before and I dont
understand what the issue is. If the boat has a motor I can almost guarentee
its grounded somewhere to the hull weather its inboard or outboard. Would
someone actually go through the trouble and expense to isolate the electrical
system from the hull? That would take a lot to do!!

The debate is long & I'll stay out of it for now, however you are
mistaken Cred about "almost guaranteeing" engine electrics are grounded,
indeed most proper marine engine electrics are not.


How can an electrical circuit be made if there isn't any ground?

It's as expected, by a second wire going back to earth.

Say alternators there is only two connections to the alternator case &
therefore the engine block itself?? The fields are usually controlled by
the regulator earthing them back to the negative side of the battery via
the case/block & earth strap, insulate the second slip ring bush from
the case (the same as one is already) & include an extra light earth
wire so now the fields are still "earthed" to the battery but you've cut
the case/block etc out of the circuit & obviously you no longer have an
earth strap from the battery to the block.

Likewise the starter, it's only convenience that they don't require two
wires,& again it's only because one set of starter motor brushes are
earthed to the starter case that current can get to the block, insulate
then as the delivery set of brushes already are & then the case is above
ground. You then need an earth strap direct to a terminal on the starter
instead of the engine block.

Most larger proper marine diesels have all their electrics above ground
with specific earths included in their wiring. Given spark engines are
not really "proper" :-) marine engines, we're unaware of any that have
such a system.

The biggest problem is leaking currents to the block & hence the
stainless prop shaft with a bronze prop attached, bad enough but add a
steel hull & .........



K