Outboard help

[Jimmyt]

Was still editing when you replied - sorry.

I believe those are specs for the ignition system and are not relevant to starter current.

[macowneril2015]

I think I may go with 0 awg and have no issues. So since the original battery cables (ones attached to engine) are 4 awg how does one connect the 0 awg end to the 4 awg end? I really appreciate everyone's help it is very odd that it took a year to start acting up. Also not sure if anyone can shed light so I would need to replace the run for the positive to the battery and the run to the engine as well.

[Jimmyt]

Normally, the perko switch would be your point of connection for the leads from your battery banks to the outboard leads.

[Jimmyt]

To you question regarding why it took a year to surface, I can only guess without seeing it. Marginal wire sizing, poor crimping of connections, poor quality connections, results in heating at the connections. The heat causes movement and corrosion, which increases resistance and causes more heating, till the corrosion and mechanical connection get too poor to allow sufficient current transmission.

But, only a guess.

Starting application is an oddity, since the peak load only lasts a few seconds (typically). Not much time to heat things up. So, you can get away with scrimping on wire size - until something goes wrong with the motor and someone stands on the starter for several minutes. Now, you've turned this short Duration load into a continuous load...

[macowneril2015]

Normally, the perko switch would be your point of connection for the leads from your battery banks to the outboard leads.

Okay that makes sense. I wish my original battery cables ran farther than under the motor well drain bowl in the transom. I have the ground or negative running the entire length but the positive runs from original cables to switch then back.

[Jimmyt]

Normally, the perko switch would be your point of connection for the leads from your battery banks to the outboard leads.

Okay that makes sense. I wish my original battery cables ran farther than under the motor well drain bowl in the transom. I have the ground or negative running the entire length but the positive runs from original cables to switch then back.

That is typical for the ground as it doesn't go through the perko switch. A negative bus or negative terminal would be a good way to join them.

[macowneril2015]

New wires and clean connections seemed to do the trick I appreciate everyone's help and patience with me while we worked through this.

[Jimmyt]

New wires and clean connections seemed to do the trick...

That's great! Glad you got it working!

[Massey]

I know this has already been fixed, and that is great! … but there was a comment that always gets me. Up a few posts there was talk about using 0 gauge wire… why? What size engine are you starting? Too much of a good thing isn’t always a good thing. 0 sized wire isn’t even needed to start a modern V8 diesel in a pickup truck, 2 gauge does just fine for that job, and here you are trying to start a 1 or 2 cylinder outboard with wire used to start a semi engine! While 0 gauge wire can handle a boatload of current, it’s way overkill for an engine that will only draw 50-80 amps to start… and 4 gauge wire can easily handle 3x that much current. You would be better off making sure all connections are good, there is no corrosion and the battery and starter are in good health. A hot wire while starting is a sign of high current flow, but high current flow is not always fixed with larger wire.

You should be able to look up the engine’s specs and see how much current is expected from the starter…. This is what you gauge the wire size on. Get a size that will cover the required amps, and still have some growing room. If you do this and there is still a hot wire, or the motor is struggling to start that my friends isn’t a sign you need bigger wires, or more batteries, that is your motor asking for help!

Marine wire connections (especially salt water) should be soldered or come pre assembled and sealed. Crimps alone are not going to prevent corrosion, they will accelerate it. When making crimp/solder joints make sure the copper of the wire and the crimp end is bright and shiny all the way through. Use a good quality solder flux and make sure to fill the connector up, not just solder around the top. I like to also used a self sealing heat shrink to further seal up the solder joint. This works much better than electrical tape, or an open joint. Same thing on the battery side, don’t just use crimp type connectors, use solder, and seal it up.

[Jimmyt]

My $.02.

If you are installing wiring in a vessel, you should try to comply with ABYC E-11 AC & DC Electrical Systems on Boat. What might work, and what complies with the standard are not always the same. Should you have an electrical fire, your insurer may not look favorably on a bunch of non-compliant wiring.

Of course, Macgregor didn't always play by the book either. But, as you go through your boat making wiring modifications, it might be prudent to follow the standards. Neither 4ga, nor 2ga appear to meet the standard for an 80amp circuit at 36 ft length. This might be acceptable for automotive use, and it might work (automotive has its own standards - which I didn't check since we aren't talking about wiring a car).

We never got a detailed schematic, with wire lengths, nor did we ever know exactly what the starter current requirement was. I looked pretty hard for a starter current spec for a 50 hp outboard and came up empty. Maybe you had better luck. But, based on the limited info we had, 36 ft, critical load, 12v, and using your 80amp load, I get a 1awg wire size to be compliant. Rounding up to 0wg would not seem unreasonable, given the level of certainty.

He got away with 4ga for awhile. It eventually failed. While I don't know for sure, I would guess it failed at the connections as you are thinking. But, it wasn't compliant. There are reasons the standard is on the stout side I'm sure.

Absolutely agree with you on the connection discussion. Great points.

As always; your boat, your rules.

[Massey]

If this were a circuit that would have a 100% duty cycle @ 80 amps, and the length of 36 feet then yes a 0g wire would be required. This isn’t the case with a small boat unless someone really needs help running wires efficiently. Even a 36’ boat is unlikely to need 36’ of wire for the starting circuit, and chances are a 36 footer would be an inboard anyway. This wire will have a duty time of a couple seconds while cranking which is when the most load will be put on it, and after that when the wires are used to charge the batteries they will not be charging at a full 80 amps, it will be something closer to 5 or 10, well within the limits of 4g wire @ 100% duty cycle. Another problem you will run into using a wire that is too large is the losses due to resistance. Yes a AA battery can light a small lightbulb through a 0g wire, but take the same bulb and same battery, same length of 20g wire and the lightbulb will be brighter as the 20g is better suited for the work. The same thing will happen with the starting and charging circuits of an outboard motor. Too large of a wire can induce losses due to the resistance. Again too much of a good thing isn’t always a good thing.

[Jimmyt]

Yes a AA battery can light a small lightbulb through a 0g wire, but take the same bulb and same battery, same length of 20g wire and the lightbulb will be brighter as the 20g is better suited for the work. The same thing will happen with the starting and charging circuits of an outboard motor. Too large of a wire can induce losses due to the resistance. Again too much of a good thing isn’t always a good thing.

Your boat, your rules.

Looks like the general consensus is; starter circuit wiring should drop one volt or less under cranking load. Less drop is better during starting as the motor will spin faster and all of your electronics will have closer to 12 volts to work with. Every on-line calculator, sizing chart, etc that I have found shows lower voltage drop for larger wire. If you think the larger wire gives a higher voltage drop for starting at approximately 80 amps, then use smaller wire on your boat. I have been unable to find any support for that position, but I'd rather buy you a beer and talk about your boat rebuild than argue with you about battery cables. I'm out.