power drop from battery

[fisherguy123]

I would like to re-locate my starting battery.It is presently about 2 ft from my motor and I plan to move it to a better spot in my boat . I will be using about 10 ft of 8 gauge copper wire. Does anyone know if there will be a noticeable power drop from my 650 mca battery. The motor is a 1980 50hp merc with tilt and trim ? Will I have to go to a bigger battery ?
thanks

 

[JB]

Re: power drop from battery

Battery will be okay. I think you will need much bigger wire. I would use at least 1-0 battery cable.

There are formulae for deciding what size wire (minimum0 to use. There is no maximum. . .the bigger the better.

 

[dingbat]

Re: power drop from battery

I would like to re-locate my starting battery.It is presently about 2 ft from my motor and I plan to move it to a better spot in my boat . I will be using about 10 ft of 8 gauge copper wire. Does anyone know if there will be a noticeable power drop from my 650 mca battery. The motor is a 1980 50hp merc with tilt and trim ? Will I have to go to a bigger battery ?
thanks

A voltage drop is the result of the carrying capacity of the wire connecting the battery to the equipment. Increasing the supply doesn?t increase the carrying capacity of the wire.

To determine a voltage drop, you need to know the current draw and the total length of cable between the battery and the equipment. In your case, you?re increasing the length of cable from 2 ft to 10ft which is a significant increase in the length of the circuit.

Starters and trim motors are high amp draw items. Your 8 gauge cable is not going to cut it.

http://www.alternatorparts.com/wire_size_chart.htm

 

[sasto]

Re: power drop from battery

#8 at 10 feet will carry 20 amps with little voltage drop.
#6 will carry 30 amps at same distance.
# 4 will carry 50 amps.
#2 about 100 amp.
1/0 will easily carry 150 amps.

If I remember the calculations correctly.
Maybe find an online chart.

Good Luck!

 

[Silvertip]

Re: power drop from battery

I mean no disrespect but here again is an example of where applying a little logic would indicate why 8 gauge wire is not going to work. Look at the size of the current battery cables! Why do you think they are the size they are? What would lead you to think you could not only move the battery 10 feet away and at the same time get away with using much smaller wire. And that 10 foot distance is actually 20 feet because that circuit makes a round-trip FROM the battery, to the engine, and then BACK to the battery. As was pointed out, any battery will deliver its full capacity to whatever loads are connected provided the interconnecting wire is large enough. If the wire is not large enough, that wire becomes a heater and in a severe case of undersizing, as is the case here, it would likely go up in smoke.

 

[halas]

Re: power drop from battery

I would like to re-locate my starting battery.It is presently about 2 ft from my motor and I plan to move it to a better spot in my boat . I will be using about 10 ft of 8 gauge copper wire. Does anyone know if there will be a noticeable power drop from my 650 mca battery. The motor is a 1980 50hp merc with tilt and trim ? Will I have to go to a bigger battery ?
thanks

#4 copper wire will be plenty for the 50 Hp starter. Make good connections with soldering if possible or with quality wire lugs and heat shrinking insulation.

 

[JB]

Re: power drop from battery

#4 copper wire will be plenty for the 50 Hp starter. Make good connections with soldering if possible or with quality wire lugs and heat shrinking insulation.

Disagree strongly. 1/0 minimum. That starter may draw 200 amps at stall.

 

[halas]

Re: power drop from battery

Disagree strongly. 1/0 minimum. That starter may draw 200 amps at stall.

I protect my starting circuit for my 115 Hp. outboard with a 60 Amp in-line fuse. Never had an issue of burned out fuse from overload by the starting circuit. I would never go bigger than 60 Amp because of the increased fire hazard on boat caused by high current.

For a 50Hp. outboard's starter motor I would recommend 4 gauge wire and a 40 Amp inline fuse.
If the 40 Amp blows for some reason it can be upgraded to a 60Amp fuse with the same #4 wire.

200 Amp onboard is outrageous for a small outboard.

 

[Silvertip]

Re: power drop from battery

How do you hook a battery cable to a 40, 50 or even a 60 amp fuse. If you are connected in the starter solenoid "S" connection then what you have is overkill. If you are connected in the actual positive battery cable, then there is no way that fuse would hold under starting conditions.

 

[bassman284]

Re: power drop from battery

Nice link, dingbat. Thanks.

for fisherguy, have you ever used a set of 8 guage jumper cables and get no more than a grunt out of the starter on the dead vehicle? That's why everyone is saying 8 won't cut it.

I guess you could try the 4 and see if it does the job. Not like you're going to get stuck in the middle of the lake or anything. Personally, I would go no smaller than 1 just to be sure.

 

[Silvertip]

Re: power drop from battery

For JohnnyRudes, 4 gauge is the MINIMUM recommended cable size up to 10 foot run for engines from 60 HP through V8 models. More than that length and you are looking at 2 or 1 gauge. There is a reason for that cable size and it is not because the starter draws less than 60 amps.

 

[halas]

Re: power drop from battery

How do you hook a battery cable to a 40, 50 or even a 60 amp fuse. If you are connected in the starter solenoid "S" connection then what you have is overkill. If you are connected in the actual positive battery cable, then there is no way that fuse would hold under starting conditions.

It can be done. Use quality wire lugs and professional grade heat shrinking tube. I do it to all the time on any circuit for the boats I wired.
Here is an example I did with 40 Amp inline fuse directly in series with the deep cycle battery at the bow. The starting battery in the same place under the bow has the same kind of automotive fuse from Napa but in 60 Amps.
My circuits are protected wit the proper fuse, sized to the wire and the load of that particular circuit.
The 115 Suzuki that I use on this particular boat had never blew that 60 Amp fuse. The outboard has a much smaller starter motor than an automotive starter would be.
The windings on relatively small outboard starter would be burned out fast by the current that turns over the starter of a cold Ford V8 for example.

 

[fisherguy123]

Re: power drop from battery

thanks for the replies....that`s why I ask for advise on this ...I ain`t no electrician. I thought that 8 gauge would be big enough cause that is what a lot of booster cables are....now I know that I`ll need at least 4 gauge or heavier and a big fuse as well. .... I will solder and heat shrink as well.

 

[Silvertip]

Re: power drop from battery

First: CHEAP jumper cables have 8 gauge wire. CHEAP jumper cables melt in a heartbeat if you crank on the engine for anything longer than a few seconds. Just ask the dipstick that borrowed mine at the golf course last summer. Left them by my car in a melted heap. Yes - outboard starters are smaller than auto engine starters. Big outboard starters are larger than small outboard starters. Have a hard to start situation where you need to crank for a bit and that 60 amp fuse and the wire will go bye-bye. Why on earth do you think there is no fuse in the positive battery cable? Adding one only creates a potential problem where there isn't one.

 

[fisherguy123]

Re: power drop from battery

halas says to use a fuse and silvertip says not to......I`m not sure what to do now other than use some very large wire !!!

 

[Josh P]

Re: power drop from battery

i have never saw a fuse on the main power wire to the starter..maybe the s wire but not the main power wire.... i here have to agree with silvertip.

you need to figure out what the current draw is to figure out proper wire size here is a link scroll down to figure out you proper wire size per abyc standards.

http://www.acbsphl.org/Tips_and_hints/ABYC_Wiring.htm

 

[jlinder]

Re: power drop from battery

I guess the big question is what does the starter on the 50HP outboard draw? From the postings it appears the opinions are that it can be less than 40A to a lot higher (100A peak?)

Would 8 Gauge burn up on 40A or less draw? No. Would 8 gauge burn up with a 100A draw. Maybe not if the engine started quickly, could be if you had to crank for a bit. I wouldn't use it.

These are all good questions but in the absence of solid info on how much the starter can draw why not just play it safe and do it right? How much extra does the heavier wire cost?

Think of this - a lighter wire will deliver less voltage to the starter causing it to strain more, run a little slower, and draw more current. A heavier wire will give you better performance.

Without knowing the actual current draw my best guess would be that 4 GA is the minimum, 2 GA would be better, but 0 GA would be the better way to go.

 

[Silvertip]

Re: power drop from battery

I don't understand why this is so hard for people to get a grip on. One would think that the engine manufacturers install large gauge battery cables just becuase they have an abundance of expensive large guage battery cable laying around. The simple fact is they do it because it is necessary for your safety.

If one does a search for "outboard motor current draw" there are ample "real world" examples of those numbers. But to save you some trouble, a free running motor may draw 30 - 40 amps which is well within the current handling range of 8 gauge wire. The problem however are the words "free running". What is missing is 1) in-rush current and 2) no load. The inrush current can be 300 amps for a very short period and then under load (as in cranking with plugs disconnected but not removed) my be in the 150 amp range "on average". Obviously some more and some less. What you can get away with is a "personal" choice. What you tell other folks they "can get away with is bad advice" because you simply don"t know what they can get away with.

 

[jlinder]

Re: power drop from battery

I don't understand why this is so hard for people to get a grip on. One would think that the engine manufacturers install large gauge battery cables just becuase they have an abundance of expensive large guage battery cable laying around. The simple fact is they do it because it is necessary for your safety.

If one does a search for "outboard motor current draw" there are ample "real world" examples of those numbers. But to save you some trouble, a free running motor may draw 30 - 40 amps which is well within the current handling range of 8 gauge wire. The problem however are the words "free running". What is missing is 1) in-rush current and 2) no load. The inrush current can be 300 amps for a very short period and then under load (as in cranking with plugs disconnected but not removed) my be in the 150 amp range "on average". Obviously some more and some less. What you can get away with is a "personal" choice. What you tell other folks they "can get away with is bad advice" because you simply don"t know what they can get away with.

Silvertip - thanks for putting some numbers on it. I had no good estimate on the current draw.

I am always amazed that cars manufacturers get away with 4 gauge. But they are trying to cut corners and counting every penny and only going about 2-3 feet.

Based on Silvertip's information I would say go with 0 gauge if at all possible, 2 gauge in a pinch, 4 gauge is a no, and 8 gauge is a HELL no.

Silvertip - do you agree?

 

[GLENN M]

Re: power drop from battery

electronically not enough power is a killer causes heat witch robs more power more heat less power.always always go with bigger wire and shortest distance.never heard of fuse in main leads to starter,fuses are for short circuits not to limit power to starter,cold flooded engine 200 amps yeah and what about when starter starts to wear out,starts needing more and more power you will be glad you have the big wire.dont fool around boating can be life or death. nobody ever died from from thier wire being to big.always factor in a safety margine if 4 will work use 0gauge you wont be sorry.ps silver is right