Putting a main fuses in

[sea hunt bob]

Looking for a little help on putting a fuse in between the battery and starter I have a 150 Johnson just trying to figure out what size fuse to put in would appreciate a little help :confused:

[Walleyed]

Honestly, I've never seen a breaker placed on the positive main between the starter and the battery, in either marine or automotive applications. However, should you want to do it, here are the steps you need to follow:

1) determine guage of the wire running from your starter to your battery. The size of this wire will determine the maximum amperage you can run over that cable.

2) Using a amp meter (clamp on style would work well in this instance), determine what your current draw is when you start the motor. A cold start will draw more amperage than a warm start.

If you are currently drawing more amperage than what the cable is rated for (you can google this), you need to upgrade your cables ASAP. If not, you can now place a appropriately sized breaker in the circuit.

However, please read the following: http://www.jamestowndistributors.com/userportal/document.do?docId=108

ABYC Standards exempt wiring between the batteries, the main battery switch and the starter motor. These wires can also burn if too much current flows through them, however, it is often not practical to provide such protection. (quoted from above linked article)

Personally, I see this as adding unnecessary complexity and points of failure to your system.

Jim

[sea hunt bob]

Reason why I want to do this is my positive grounded out and both negatives to each battery melted almost caused a fire. Thank you for your help I really appreciate it :)

[Duffman]

Why not just protect the + feed from rub thru and not have to add a fuse?

[Gerry Zagorski]

Why not just protect the + feed from rub thru and not have to add a fuse?

Agreed. Fix the problem rather then treat the symptom.

[Capt. Debbie]

Agreed.

The more complicated your electrical system - the more problems later. In line fuses fail, develop bad connections and haunt you.

Chafe protection as suggested. A battery kill switch will help. The only thing always on should be the bilge pump with 16/18 guage wire. Often the small guage wire is a fuse itself.

Never fuse a starter. The normal start current going into the starter is so high that you main fuse at 80 amps or so, will do nothing for you. Just about ever other wire on the boat will burn up without blowing it that monster. Main breaker your accessories- they sell a 40 amp main breaker and it will work fine for you. And can be reset it unlike a throw away and replace it fuse.

BTW you can not use an amp clamp on DC as suggested. It's for AC only.

And if rewire - you use boat/auto wire. The right type of wire ... It's strands are much more finer and are flexable unlike household copper wiring. Stiff wire breaks bouncing around. Look at your jumper cables and you will see.


Agreed. Fix the problem rather then treat the symptom.

[Bass_Appeal]

I dont have a fuse but a 45 amp breaker coming out off of the battery on/off switch....that should be enough to trip and break the connection ,

[Walleyed]

BTW you can not use an amp clamp on DC as suggested. It's for AC only.



Not to start an argument, but I have a Fluke 325 that quite happily measures up to 400A DC current.

There are several clamp style AC/DC meters out there.

[Duffman]

BTW you can not use an amp clamp on DC as suggested. It's for AC only.



???? Um..... No.