extended cranking trips 100 amp breaker

[sastanley]

I can no longer find an image (maybe I have one at home, I'll check), but I have a Blue Sea 8062 battery switch w/ 100 amp breaker. When I crank the A4 for a long time (like when I don't visit her often and she wants to be cranky and not fire up), I often trip the breaker after 10-15 seconds of cranking.

Is it safe to put a larger breaker in place of the current 100 amp? That leads to the next question..what is the correct breaker to install?

I also have a 100 amp fuse where my 4# wire feeds into the DC panel, so that system is protected separately. This main battery switch/breaker was an ebay find and was cheap..I've personally never seen another battery switch with a breaker in the mix.

Here is a wiring diagram..it is old, but the engine/battery circuit is accurate.

[Dave Neptune]

Shawn, a 100 amp seems low to me. I seem to remember the A-4 drawing in the neighborhood of 150, especially if the batteries are not "topped off". I'm sure someone will chime in with something more accurate than a "60's" memory.

Dave Neptune

[BunnyPlanet169]

Shawn:

For better or worse, ABYC doesn't require circuit protection in the starting circuit. Meaning, you could wire directly from the "C" on your switch to the starter. The risk is it's unprotected.

I have a 150A fuse in my starting run, and have never let the smoke out of it. You could put the same in and feel safer....

[sastanley]

Jeff..I see...that may be the easiest solution...thanks for the picture.

From the few tables I've looked at, it looks like I need to up the wire gauge to 2# if I go higher than 150 amps for my ~20 foot run from starter to the main bus...so I guess we'll start at 150 and see how it goes. It might be 15', but I'd rather err on the side of caution and remember the rule...fuses and breakers protect the wiring from overheating and fire..an oversized fuse does not adhere to this rule.

Dave, I also read somewhere on here that the A4 amperage draw was more than 100A. In the summer when she starts up in a few seconds, I never have a problem..when it is cold and the engine has been dormant for a few months, she needs more cranking, and hence the breaker trip.

[BunnyPlanet169]

How far from the G24 battery to the starting terminal? At $5 per foot for #2, you might be better off with a direct run from the battery, and another switch ($25 BlueSea 300A).

[BunnyPlanet169]

This brings up an interesting can of worms, sorry.

ABYC doesn't require circuit protection in a dedicated starting circuit, I.E. battery + to starter terminal. You don't have that (because you go to a 1/2/both first). Further, ABYC wants circuit protection within 7" of a battery.

Not critiquing, just sayin'....

[JOHN COOKSON]

If you have an electric fuel pump have you tried hot wiring the fuel pump to prime the fuel system before you try to start the engine after it has been "dormant" for awhile?

TRUE GRIT

[hanleyclifford]

Shawn the A4 pulls 130 amps for the starter. I use a 150 amp breaker in the negative side and #2 cable throughout.

[roadnsky]

Shawn the A4 pulls 130 amps for the starter. I use a 150 amp breaker in the negative side and #2 cable throughout.

+1
150A on the starter, although my wire is #4. (The run is about 3')

[sastanley]

Jeff, the run is about 15'. I have no issue with opening a can of worms..one nice thing about this forum..we can open it and have a civil discussion. I am asking questions because I don't know the answers.

I started the re-wire of the boat when I moved the batteries and added the new 12v panel & 1-2-all switch..Older C-30's like mine had the batteries in the engine box and it was only a few feet & there were no fuses or breakers or anything. Now..the run is a lot longer, but one of the reasons for moving the batteries to stbd was to balance the boat..older boats had a notorious list to port (2° or so) because all the batteries & furniture were to port. The newer boats have the batteries and electronics to stbd to even things out...which is the route I went..now I have to deal with the fallout from that, which is long runs around to the engine.

John, I have a mechanical fuel pump. I am not quite sure why I had trouble starting it..I primed the mech. fuel pump prior to starting..it is possible with batteries that only have a small solar panel now in the winter shade were not up 100% and the resistors in front of the coil made the voltage too low. I am gonna let everything sit for another few months and try again..the plan is to ONLY change the spark plugs..I wonder if they just don't like sitting. After lots of cranking, as soon as I started pulling plug wires and re-seating them, she fired off..maybe some 'spark plug' goop in the boots to make sure I have a good connection. That is another whole issue..I shouldn't need extended cranking if everything is in good order.

In the meantime, I am gonna add a 150 amp fuse into the circuit and move the 4# that is on the starter over to the common on the battery switch from the main bus.

[joe_db]

My starter is around 125-130 on the meter. A 100 amp fuse is going to blow for sure.

[sastanley]

OK...what about a Blue Sea 7079? If my schematic is correct, the 100 amp breaker that is integrated into the 1-2-both switch should now be eliminated from the mix, since the starter circuit will now be from the common post with the 7079 in between that and the starter lug?



Hanley, I also don't understand the difference between putting the breaker on (+) or (-) side.??

[joe_db]

150 amps should do the trick. I have never seen over 130. You could go 175 for more headroom.

[sastanley]

150 is as high as that line of breakers go..the breaker is about the same cost as a fuse holder + $20 fuse.

[Marian Claire]

Shawn: Thanks for this thread. Sounds like I need a fuse. As best I know it is the original, late 60's early 70's, "home designed" wiring on the MC. Short 2.5 ft run from batteries to 1/both/2/off and 3+ ft from switch to early starter. She usually cranks in 2 to 5 seconds. But unprotected I would never know I had a problem till I had a big problem. Years ago I installed the Moyer recommended fuses on the boat.
Dan S/V Marian Claire