#4 gauge wire for starters?

RickS · #1 10-17-2006, 08:28 AM

I used no. 4 gauge wire for the Skytech starter and ground on my XP-360 based on the allowable current draw of 130 amps in open air or 100 bundled as indicated on a helpfull chart I got from somewhere.
Well after looking at a couple other projects at the same stage as mine I noticed they are using no 2 and also my Mooney has cables big enough to light a city it seems but I thought that was for the ancient starters only.
What shall I do?
Will the no 4 wire get too hot and smoke on a hard start cold morning?
Thanks in advance.
Rick

f1rocket · #2 10-17-2006, 08:57 AM

No, your #4AWG wire will work just fine to your starter. The current draw is for a very short duration.

Now, for the ground wire, I prefer to use flexible bonded braided straps from B&C. THis wire is subject to engine vibration and I've seen others have problems with this wire breaking, especially if you solder the connectors on the end. You may or may not ever experience a problem with this wire, but you might consider swapping it out for a BBS cable.

Mike S · #3 10-17-2006, 09:02 AM

No.4 seems a bit light, however I am not familiar witht the current dray of the Skytech starter.

You should probably start with the starter mfg info-------and dont forget that the length of run is a big consideration. You will get something like "# 4 wire for runs x feet, #2 for runs of x feet. ETC.

Plan for the max draw, not the min.

Mike

frankh · #4 10-17-2006, 09:13 AM

Quote:

Originally Posted by f1rocket

No, your #4AWG wire will work just fine to your starter. The current draw is for a very short duration.

Now, for the ground wire, I prefer to use flexible bonded braided straps from B&C. THis wire is subject to engine vibration and I've seen others have problems with this wire breaking, especially if you solder the connectors on the end. You may or may not ever experience a problem with this wire, but you might consider swapping it out for a BBS cable.

is another inexpensive approach for crossing the vibration isolation of the engine mount. I prefer crimped connectors but your welding shop can crimp these on for you if you don't have access to a crimper. Welding cable is very flexible unlike the teflon coated stuff.

Tip...Make friends with an electrician....They either have or can get baterry cable sized crimpers and the lugs should ba available from Home Depot.

Of course there are those that are reading this in horror about cheaping this part of the build. Truth is though it will work just fine.

Frank

f1rocket · #5 10-17-2006, 12:01 PM

As an additional comment, I use a #4 wire from my starter contactor to my B&C starter on my IO-540. The engine turns right over and the starter is only engaged for less than 10 seconds. You can run a bigger wire but if you already have a #4 run, I wouldn't worry about it.

I also bought a large battery crimper from NAPA for my big terminals, and still choose to go with the BBS. Just personal choice. If this ground wire breaks, it makes for a tough time to track down the problem, particularly if it goes intermittent, which it likely will do. The BBS are cheap and custom made for you based upon your dimensions and clocking instructions. Cheap insurance in my mind, but I concede that many others have crimped/soldered their own ground cable just fine.

sprucemoose · #6 10-17-2006, 12:48 PM

Rick,

I'm going to disagree with everyone who says that 4GA is OK in your installation. When you say you have a Sky-Tec, I assume you mean the flyweight model. This starter uses a permanent magnet motor design, which has a much higher current draw than a starter with a wound-field motor, such as the B & C. Depending on the size of battery you are using, and the type of prop, you might be inviting starting problems.

I would use 2GA. You can get 2GA welding cable from a welding shop, which is much more flexible and easier to work with than 2GA tefzel wire.

David Clifford · #7 10-17-2006, 02:15 PM

Quote:

Originally Posted by sprucemoose

Rick,

I'm going to disagree with everyone who says that 4GA is OK in your installation. When you say you have a Sky-Tec, I assume you mean the flyweight model. This starter uses a permanent magnet motor design, which has a much higher current draw than a starter with a wound-field motor, such as the B & C. Depending on the size of battery you are using, and the type of prop, you might be inviting starting problems.

I would use 2GA. You can get 2GA welding cable from a welding shop, which is much more flexible and easier to work with than 2GA tefzel wire.

I have to agree with this also. We used 2gauge welding wire from a welding supplier on my Cozy MKIV powered by XP IO-360, which was the recommendation from several experts in the field. I found some really nice terminals from Hamilton Marine http://store.hamiltonmarine.com/browse.cfm/2,61.html for this wire at a good price. Power comes from two Oddessy 12V batteries.

647jc · #8 10-17-2006, 02:28 PM

Van includes #2 gauge wire in his wiring / harness kits for this purpose. He also sells #2 gauge wire $33.80 / 10 ft.

J.C.

f1rocket · #9 10-18-2006, 05:44 AM

I have to apologize to this thread for my mis-information. I went back and checked and I indeed did use 2AWG wire to my starter, not 4AWG. I confused that wire with the wire running from the alternator, wich is 4AWG. Sorry for mis-leading you.

As it relates to the starter, if the Sky Tec does indeed pull more current than the B&C, (I don't know if it does or doesn't), then that's just one additional reason to get rid of the Sky Tec. I had nothing but problems with mine, which was new from Bart on my Aerosport Power engine. If you use electronic ignition and you get a kick back, you will destroy the permanent magnets inside. Also, the Sky Tec couldn't pull my engine through the first compression stroke during starting without me turning the starter on and off. After messing with this for a year, I pulled the Sky Tec and installed a B&C starter. Man, what a world of difference.

BTW, sorry for the thread steal too!

sprucemoose · #10 10-18-2006, 10:34 AM

Randy,

Your observations about Skytec starters are spot-on. A kickback can not only damage the guts, but in my case, the entire cast housing cracked from one end to the other.

This issue has been done to death, both here and on the RV List. Bottom line is that if you are running one of the new, smaller batteries (ie. Odyssey of Panasonic) and a lightweight prop, then the flyweight Skytec is not a good starter to use. Especially if you run 4AWG wire for the starter (there- brought it back home.)