Wiring kit cost for A4

[alcodiesel]

Hello all, with nothing left to tweak on my boat it began to bother me that the alternator couldn't put as solid a charge on the batts as plugging in to shore power. So I removed the ammeter and installed a V meter and directed the alternator out to the B+ on the starter. Works great.

Doing the job highlighted what a mess the engine wiring is. I am amazed at how reliable she has been.

Ok, so I'll pick up one of Don's kits. However $350! Holy shrink wrap! For wire and crimp terminals! Am I missing something here?

[Dave Neptune]

Yes the cost does seem a bit high for what you get however the reason these kits exist for both auto and marine use is that it saves a huge amount of time and fiddling. I worked on a few Jaguar's dropping in small block Chevy engines. The first one I wired myself the next two I plopped down the money and saved a great deal of time and such.

The nice thing with the MMI kit is that it follows the original color coding which is a help when a novice is using the manual you know what wire is what by color and not tracing. Time vs ease and money.

There is also a wire "bundle"" made in a couple of configurations just for wiring engines, lights and accessories. They are a single round bundle with various gage wires for each circuit. The wire is about a 1/2" and the larger with more wires is about 5/8" diameter. It makes doing the runs easy from one end to the other. I think they were 7 wire and 9 wire bundle in a nice white cover. That's what I used as I had some left from rewiring a couple of dune buggies.

Another is to just start wiring by eliminating the "trailer plug" one wire at a time. This way you can customize to your set up and desire.

Dave Neptune

[ndutton]

What Dave said.

If sourcing the marine grade, tinned wire of the proper color, wire gauge and length yourself, I expect you'll find the cost - - including time investment - - to be a wash and in the end you'll have wire and terminals left over due to package quantities not to mention you won't have MMI's excellent step by step, wire by wire instructions.

However, there may be other reasons to blaze your own trail rather than use a stock kit. In my case I had greater loads on some wires requiring a greater wire gauge to mitigate voltage drop (dual electric coolant pumps adding 4 amps to the ignition circuit that already had an electric fuel pump for example. My ignition purple wire is now 10 gauge). I also had additional wires in the engine harness not included in a standard kit such as fuel gauge senders for dual tanks and gauge illumination from the navigation light circuit. Finally, my wire lengths were a little longer than the MMI kit.

[alcodiesel]

OK, that was all I needed to order the harness.

[alcodiesel]

Perhaps I got a little carried away cutting out the harness. What is this yellow wire coming out of the alternator? I thought it was the excitor but don't see it on the Atomic schematic.

[ndutton]

It is the exciter, goes to coil + post.

[alcodiesel]

Dang, Neil, that was fast service. Thank you.

[ronstory]

... and for future reference, here are most of the alternator wiring connections for marine stuff.

[alcodiesel]

This engine was wired in a way I do not find on any schematic: R on the starter solenoid to coil +. What is that?

[ndutton]

That is an old school resistor bypass used as a starting aid and as far as I know, never part of a factory recommended Atomic 4 wiring scheme. I'll research it a little to be sure it was never recommended.

[jcwright]

Hello Bill.

This paragraph from the MMI instructions for the wiring kit mentions the R terminal I think you are referring to:

"On late model engines with Delco starters, there is an "R" terminal on the rear face of the starter solenoid which functions as an
auxiliary contact; meaning that it is energized only during the time the starter is engaged to start the engine. By running a lead
from the "R" terminal to the same terminal on the oil safety switch to which the pump connects, it’s possible to supply power
directly to the fuel pump while the engine is being started; otherwise, power to the pump will be provided in a second (or two) as
oil pressure raises past 10 psi. "

Hope this helps.

Jack.

[alcodiesel]

Neil, It looked like original wiring and I was guessing something like that. No need to research. This was an "Inquiring minds want to know" kind of thing.

Thanks Jack, it ran to the coil.

[ndutton]

The R terminal has been used by a few forum members for different reasons. As jack said, some use it to give an electric fuel pump a pre-start jolt, I've used it in the past to get a single wire alternator to start charging without having to rev the engine up (I don't any more) but as yours was wired, it gives a coil with a resistor in line a higher voltage when starting. In my opinion, none of these schemes are necessary for a good starting, good running A4. Can you do it? Sure. Should you? That depends on how much you like extra wires and complication.

FYI, my Westerbeke A4 manual does not show anything connected to the R terminal in any of their wiring drawings.

[alcodiesel]

Thank you everyone. She is rewired. Looks good. Don't smell any insulation burning. haha! Tomorrow I'll clean everything up and start 'er up.

[ronstory]

Congrats! Got any pics? I need a bit of inspiration to tackle my birds nest.

[alcodiesel]

The cockpit gauges wiring might be able to be prettier but what a difference! Color coded. Easy to trace.
The engine wiring came out well. The harness comes out just below the blower. The oil pressure, temperature, low oil P alarm all run along the port side. The big wires all run along the stbd side. All purple or ignition wires go directly to the coil, etc.

Hung the broom from the yard arm: Clean sweep! everything worked,100%. No arcing or sparking or insulation melting. The god of electrons smiled down on me.

I get about 3/4 of a volt more charging to the batts. which was why I started the whole adventure by removing the ammeter from the circuit and went with a V meter.

I feel this is much more reliable than the 45 year old wiring- even though the old wiring caused me very little trouble- Preventive maintenance. Very important to me as my two goals are safety and reliability.

[edwardc]

Three quarters of a volt is a huge difference! Congrats!

[ndutton]

With your improved wiring and reduced voltage drop the question now emerges, do you have electronic ignition? If yes, it's time to redo your coil input voltage→coil internal resistance→ignition system current calculation to make certain you're below 4 amps current. In my experience, 3.3~3.5 amps is the sweet spot.

https://www.moyermarineforum.com/for...75&postcount=1

[alcodiesel]

Thank you. Yes to electronic ignition.

Neil, you won't come up with something else once I get the amps figured out will you?

[sastanley]

Neil's question is the exact problem that arose when I re-wired my engine several years ago. I did the exact same process you did...Ammeter delete & re-wire..next thing started blowing coils.
Just need to do a little calculation and maybe a little extra resistance.

[ronstory]

Great job and looks great. Regarding the coil, the one MMI sells has the correct resistance (~4.25 ohms) and no extra resistor to deal with.

Yes, they do cost a bit more than the everyday Napa UC14SB, but are great quality and will last a lifetime... unless, of course, you leave your ignition on with the motor off for extended times. ;^)

[ndutton]

Originally Posted by alcodiesel

Neil, you won't come up with something else once I get the amps figured out will you?

It must seem like I derive a perverse pleasure dropping little bombs into folks' projects but when something triggers a memory I figure it's better to raise the issue now rather than read about an overheated coil and engine shut down later. As I read your rewiring success, Shawn's experience came to mind.

[alcodiesel]

Just joking, Neil. Reliability is a top concern. If I need that engine to run, I need it to run! I appreciate your suggestions and help. You have always ( 6 years) been there for me. Thank you.

Here's what I came up with:


Voltage at the coil [ + ] terminal at cruising RPM 7.4 Volts

Primary winding resistance of the coil 3.9 Ohms
(terminal to terminal, [ - ] wire removed)

Recommended resistor -1.7 Ohms
No Resistor Recommended

[ndutton]

Well, you're not gonna like this. At 7.4V to the coil your engine shouldn't even be running. Years ago when we were doing testing to establish a practical trip threshold for the EWDS we found engine performance dropped off significantly just under 9 volts - - - and that was at idle! Please repeat the coil input voltage test between coil + and a solid block ground. For the re- test, twist or 'drill in' the test probes to eliminate the resistance of engine paint, grime, corrosion and rust. Be aggressive with the probe points.

While you're at it, please measure the alternator output too. It should be somewhere around 14 volts. That will establish confidence in the alternator, test technique and meter accuracy, a good baseline.

[alcodiesel]

Woah, I measured between Coil + and coil -. Sheesh, do I feel like a dummy.