Inline fuse protection for the battery cables

[Marco Flamingo]

After reading some of the posts on marinehowto.com, I looked into what it would take to put an inline fuse on my batteries, both house and starting. I have a Yamaha 50, and it seemed like a 150 amp fuse would be small enough to protect the 2 AWG wire and large enough to take the momentary amperage to start my motor.

Then I started to think about what would happen if the fuse blew. I suppose that would normally occur from abrasion (although I put my cables in conduit) or something somehow bridging between hot terminals (stuffing a lawn chair under there?). Anyway, fixing the short and putting in a new fuse might not be enough.

Wouldn't blowing a fuse on the battery while running be the same as turning the battery off? Wouldn't it blow the alternator? A $17 spare fuse and fixing a short can be done on the water, but a spare alternator? I'm just trying to put together the pro and con.

Mark

 

[BrentB]

I thought the fuse or circuit breaker protects the wire not the device, and opening depends on the amount over its amperage and the length of time

 

[thataway]

The 150 amp fuse may or may not blow. You would have to have very special quilt meant to know what the momentary load is on the starter motor.

A fuse is not called for between a battery and starter/charging circuit on an outboard. I think it is a bad idea, especially if you have a standard installation of cables. ABYC relates specifically relates to a cable or wire permanently attached to an outboard motor.

Here is the ABUC electrical code:

https://law.resource.org/pub/us/cfr/ibr ... 9.1990.pdf

Here is a diagram of what ABYC requires:

 

[AstoriaDave]

Bob,

I think the auto correct must have converted "equipment" into "quilt meant," no? One of the most abstruse auto correct examples I have seen!

BTW, I interpeted that 7 inch requirement as between the plus terminal and the fuse/breaker. That really made my simple single battery installation tight. Can not imagine a multi battery setup.

 

[thataway]

Right Dave,
These fingers may not be as nimble--and the eyes missed that before I hit the "submit".

There are exceptions to the 7"--and those involve position and support of the wiring,

I quote from ABYC: :

E-9.10. DC POWER SOURCES

a. Overcurrent Protection Device Location - Ungrounded conductors other than cranking motor conductors shall be provided with overcurrent protection within a distance of 7" of the point at which the conductor is connected to the source of power measured along the conductor.
EXCEPTIONS:
1. If the conductor is connected directly to the battery tenninal the 7 inch distance may be increased up to 72 inches.

2. If the conductor is between the source of power, other than the battery terminal, and the required overcurrent protection device, and is contained throughout its entire distance in a sheath or enclosure such as a conduit, junction box, control box or enclosed panel, the 7 inch distance may be increased up to 40 inches.

Using these criteria, even a multi battery set up is not bad--as long as you are going to the terminal, or are supported properly.