Electric Starter Wire Cable Gauge Size (Pure Copper)

BugleCoveTinBoat · Nov 24, 2024

Does anyone know the proper gauge for pure copper (not copper clad Aluminum) for my Evinrude 28 HP Speed i Twin starter to battery cable?
I suspect it would be the same (starter, draw, cable gauge) for a 25, 28, 30, 35 or 40HP OMC twin cylinder outboard.
thanks in advance,
Chris

DaleH · Nov 24, 2024

Solid cable or stranded? You should only use standed AWG cable. Starter load depends on the length run BOTH ways, to and fro, to determine the ampacity of the cable needed.

I know that OMC V6 OB starters have a peak amp draw of ~ 230 once energized and ~180 sustained. I have OEM Service Manuals at the house that likely list the recommended cable sizes, but I’m not home …

BugleCoveTinBoat · Nov 24, 2024

Thanks for the response. I understood anything that is in any kind of vehicle should be stranded wire. I also understand that solid "stranded" wire will have more capacity than copper cladded aluminum wire. I am planning on using the OMC Red Plug for my control wires. My question is about getting the power from the battery to the engine (28 HP Outboard). I'm planning on using Jumper Cable or Welding Cable wires. the length will be less than 5' (Probably less than 3'). I do not know much about the starter motor (except its over 60 years old).
So, should I use 6 Gauge (stated good for constant 200 amps) or move down to 8 or 10 Gauge?
Again, thanks for your almost immediate response,
Chris

MrGiggles · Nov 25, 2024

It's a little bit of a hard question to answer by the book, loaded current draw specs for smaller motors is not usually published.

Even the big four strokes only use 4AWG, 8AWG should be more than enough for a short run.

wmk0002 · Nov 25, 2024

I used some cheap 8awg jumper cables for my 2 stroke Yamaha 25hp. Probably not the best quality wire but I sized them based on current draw on the starter listed in my service manual and then used a basic marine amp wiring chart and run length. I figured for the cost, if they ever corrode I can easily and cheaply replace them. That said, I'm fresh water only and my motors stay in my shop whether they are on or off the boat. My motor also has a recoil starter so having that as a backup inspired me to go cheap as well lol.

OldSailor85 · Nov 26, 2024

FWIW, if you have a welding supply place around, get welding cable.

Super flexible, very-high strand count. Buy once, cry once.

They also carry all the lug-ends and may even put them on for you. How many guys have the proper tools to crimp large cables?

Pappy · Nov 28, 2024

Go larger. Believe it or not the two cylinder 28 would most likely pull more initial amps than a V6 will. I would do nothing less than 6 on this. Remember you have to measure it both ways.

Sea Antsy · Nov 28, 2024

... and if you can find some nice solder on lugs.. DON'T do it...
solder Is not the way to go... get them crimped on..

OldSailor85 · Nov 28, 2024

Sea Antsy said:
... and if you can find some nice solder on lugs.. DON'T do it...
solder Is not the way to go... get them crimped on..

Why no solder If one has the tools?

Just curious about the rationale.

Sea Antsy · Nov 28, 2024

WELL you can do a search on ABYC no solder.. or here is a clip from THE HULL TRUTH
"Solder after crimp is preferred. Most people skip it, because it takes more time and money to do it right. When solder is flowed into the connection, the conductance path between the wire and terminal is increased significantly. Might not mean much in very low current connections, but for areas where there's some current flow, the soldered connection will operate at lower temp for a longer time over just crimped.

Fortunately, crimped connections are typically left alone with little or no strain on the wire. In cases where there is any kind of strain or stress on the wire, a crimped connection will fail long before crimp and solder. However - doing a good solder job is not as easy, and plenty of them are left in a 'cold joint' condition, which is worse than no solder at all."

BugleCoveTinBoat · Nov 30, 2024

6 Gauge is good for 200 amp draw and 4 Gauge is good for 300 - 500 amps.
The question is the starter motor for my 28 HP Evinrude Speeditwin (2 cylinder).
If an OMC V6 is 230/180 amps, 4 Gauge for the 300 -500 to be safe would make sense
but, I'm not sure if 4 Gauge is required to spin 1\3 the cylinders.
Any input would be greatly appreciated.

BugleCoveTinBoat · Dec 1, 2024

Thank you all. It looks like 4 Gauge should meet the needs. At this point its unclear if I'll use jumper cable or welding cable (defiantly stranded pure copper). I do like that jumper cable is typically sold as a pair. I was in the welding supply business more than a decade ago so I'll check my old contacts there. Perhaps they have a tried and true process for the ends. (I'll be sure the ends are crimped and then soldered.) (My recollection is that welding cable is much heavier.) A shout out to Pappy, I (now) agree that a big twin might actually need the same or more oomph than (more smaller cylinders) V4 or V6. The hard decision was what is actually required and yes I understand no one here has a manual for a 1964 28HP Speeditwin nor has anyone put an ammeter on it either so, yeah a best guess and I appreciate it.
Chris @ BCTB

MrGiggles · Dec 2, 2024

The factory leads on my 98 Evinrude 50SPL (also a twin cylinder) are 6 gauge if that helps you at all.

Pappy · Dec 6, 2024

It is really not a best guess. Keep in mind we are talking 2 strokes here. Although it may not make sense (V6 vs 2 cyl) the smaller twin cylinder comes up on compression only once every 180 deg. vs the v6 at every 60deg. Add to that the fact that a lot of the smaller twin cylinder engines have a bit higher compression and you should be able to see that the hit on the starter is actually higher every revolution when trying to get the twin cylinder turning.

thill · Dec 7, 2024

I would use 4 ga. marine wire. I always choose tinned wire in boats. It doesn't cost much more. Something like these:

4 Gauge Marine Wire,10ft 4 AWG Duplex Marine Grade Wire Tinned Copper Insulated Red& Black Marine Electrical Wire for Boat/Marine/Automotive/

4 Gauge Wire-10FT Black 4 Gauge Marine Wire + 10FT Red 4 AWG Marine Wire,4 AWG Marine Grade Wire

Tinned connectors are also a must for boats, in my opinion. These are the ones I use:

10pcs 4 AWG-5/16 Stud Tinned Copper Wire Lugs, Heavy Duty Battery Cable Ends, 4 Guage Ring Terminals, UL Listed Battery Lugs Marine Grade Copper Eyelets Electrical Battery Terminal Connectors

No sense buying good wire and thin, cheap connectors.

I generally swage my connectors on. I have soldered on occasion, but I have never, ever had a problem with wires I've swaged on, but I have my own equipment. Use heat-shrink tubing with glue over the connection. These come with the tubing, but I haven't used this particular brand:

https://www.amazon.com/TKDMR-10pcs-AWG-Terminals-Adhesive/dp/B094FSTH5V/

If not sure about your connections, go to West Marine, and they can do it properly for you.

If you choose to solder, tinned wire and lugs are BY FAR better for a secure connection.

I hope this helps.

OldSailor85 · Dec 7, 2024

BugleCoveTinBoat said:
Thank you all. It looks like 4 Gauge should meet the needs. At this point its unclear if I'll use jumper cable or welding cable (defiantly stranded pure copper). I do like that jumper cable is typically sold as a pair. I was in the welding supply business more than a decade ago so I'll check my old contacts there. Perhaps they have a tried and true process for the ends. (I'll be sure the ends are crimped and then soldered.) (My recollection is that welding cable is much heavier.) A shout out to Pappy, I (now) agree that a big twin might actually need the same or more oomph than (more smaller cylinders) V4 or V6. The hard decision was what is actually required and yes I understand no one here has a manual for a 1964 28HP Speeditwin nor has anyone put an ammeter on it either so, yeah a best guess and I appreciate it.
Chris @ BCTB

Welding cable comes in different gages.

There is also DLO, or "locomotive cable", if you need some 4/0 or larger that is as flexible as welding cable.

Electric Starter Wire Cable Gauge Size (Pure Copper)

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