How to "wire" a new tachometer to the alternator

[bigoledave]

getting comical now..

This is getting a bit comical. Here is the response from the
closest contact I could find through amazon regarding hooking up the tach.



Hi dear Dave,
Thanks for your email and so sorry for any trouble.
We are so sorry that we can't find your order in our store.
Here is the picture to show the proof, please check the attachment to confirm it.
So please contact the correct seller to solve your issue well.
Because you confirmed the item, and here is the instruction of the item, you can see it and then you can know it better.
And according to your meaning, you don't want to buy the speed sensor and then you want to use the item you ordered directly, is that right?
If yes, we are so sorry, that item can't be done this.
You should need the speed sensor and then can do it.
So sorry again and hope for your kind understanding.
You can also contact your correct seller to solve your issue well.
Have a nice day.
Regards,
June
Attachments:
can't find 114-5895990-9684253.png

ahahahaha

[joe_db]

These are the directions that came with my tach. They look identical to your tach. Connect it to the coil through a 5K resistor and I am 99.9% sure it will work. No one at Amazon is going to have the slightest clue.

[bigoledave]

i did that---no luck

I have tried that ....with no luck. See my previous post about it.

I will try it one more time.

thanks

I was communicating with the place in China...not Amazon.
Amazon gave me a link.

[joe_db]

I have tried that ....with no luck. See my previous post about it.

I will try it one more time.

thanks

I was communicating with the place in China...not Amazon.
Amazon gave me a link.

Do you have it on the 2 setting as shown? If the speed ratio is 96 or 112 or similar, it will probably always sit on 0.
Are you sure you are on the negative side of the coil?
The thing might just be dead if it does nothing.

[ndutton]

I'll repeat, and now considering the budget, I'd spend it on a new alternator before anything else without regard to an AC tap or 'W' terminal. Next, I'd trash this tachometer or put it in the box of shame as a lesson learned. Everyone on this forum has learned lessons the same way so welcome to the club. Finally, when you decide you really want a tachometer, if ever, give Ken a call at Moyer Marine and order a proper tachometer that is designed to connect to the coil. You'll get a quality gauge, it will be pretty much plug and play and the instructions won't be in poorly translated English. Sure, it will cost more than the Chinese cheapo you're struggling with now but in the big picture of boat ownership it's not that much.

One of Dave Neptune's prophetic rules is Do it right and cry once ($).

You'll be glad you did.

[joe_db]

You WILL pay, the choice is what. Your time or your money, the cheap stuff takes a lot of experimenting and the Moyer stuff just works but costs more.

[bigoledave]

My new sailboat instruments

I am buying BOIH of these new "instruments" for Moonduster:

1) A very S I M P L E tach that is perfect for my needs. I may even mount it in the engine bay.

https://www.amazon.com/Maintenance-Tachometer-Replaceable-Motorcycle-Paramotors/dp/B07PMJH7QV/ref=pd_bxgy_img_sccl_1/146-2275669-4913428?pd_rd_w=nWtiR&content-id=amzn1.sym.6b3eefea-7b16-43e9-bc45-2e332cbf99da&pf_rd_p=6b3eefea-7b16-43e9-bc45-2e332cbf99da&pf_rd_r=S6SV22DRCZ7DYJYRKTY9&pd_rd_wg=o5Pwj&pd_rd_r=40a30d41-6b12-4bdd-b13d-37103ea19001&pd_rd_i=B07PMJH7QV&psc=1

2) A cool sailing instrument that will cover the big tach hole
and add sailing "knowledge:https://www.amazon.com/dp/B00FGCTMT2...p_imgToDp&th=1

[bigoledave]

Eureka--I found a 12v COIL driven 4k tach for $60

Ebay!!!

I am still keeping my order for the small tach that gets it's pulse
from a spark plug wire in case this has problems. Anyway..no
more adding "speed sensors" or paying people to hack my unloved
blue alternator (which has given ZERO problems in the 43
years on the boat.)

Here is what I found...perfect if it really works...coil sensing...the
range I want ..and the size I want....and inexpensive too.

https://www.ebay.com/itm/132907369726?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D3b2de4bf3f694b7699d9c35ab7c1bcd0%26pid%3D100675%26rk%3D2%26rkt%3D15%26sd%3D195049562849%26itm%3D132907369726%26pmt%3D0%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3A7029dad5-dfd2-11ec-91b1-a277b9a2a488%7Cparentrq%3A1342ad9d1810ab9708d684e2fffad6f6%7Ciid%3A14

[bigoledave]

Eureka----NEW tach, NEW alternator

Greetings,

Long story..(read the old posts if you like.)

I have found a NEW tach with IGNITION COIL sensing

..and

I have found a NEW alternator that "fits Atomic Four"

Both are solutions which started with me buying a cheap tach that
seems to NOT work with coil sensing and looking at how to get
it working with my very old alternator/separate regulator.

During testing to see if I could that combo working, the charging
functions completely stopped. Not sure if me poking around the
coil negative terminal caused this or.... it was a verrry amazing coincidence.
Either way..I then had a tach that I could not get to work, an old
blue painted alternator, a bunch of field and armature wires,
an electro-mechanical regulator and...and....I was finally ready for
an all new "system"...charging and RPM displays.

So....I searched A LOT of sources..Ebay..auto supply stores..
Amazon....etc.etc.

Amazingly..I think I have found solutions!...a $100 alternator with
a "one wire" connection.....and a $50 COIL SENSING 3000 RPM
tach.

Both are on the boat and LOOK to be great as far as fit is concerned.
I plan on hooking them up in the next few days and will post
results and pictures.

Cheers

https://www.ebay.com/itm/254384243528

https://www.ebay.com/itm/284470973289

[ndutton]

It may seem like an off the wall question but . . . .

3) I have an Indigo electronic ignition.

. . . . what is the output voltage of the new alternator? Depending on the answer it can be a VERY important question.

Also, with the larger case size of your new Delco 10Si alternator there may be a small fitment problem that is easily solved with a grinder. These posts describe the remedy:

https://www.moyermarineforum.com/forums/showpost.php?p=114256&postcount=18

https://www.moyermarineforum.com/forums/showpost.php?p=117823&postcount=3

[bigoledave]

Reply....voltage question and fitment

It is described as 12v....so ..ok!

New Alternator fits Universal Atomic Four 4-Cyl 12V 63 AMPS CW 64 65 20037

I loosely installed the alternator (no bolts) and it looks good!!

Thanks for your comments

[ndutton]

It is described as 12v....so ..ok!

My Delco 10Si alternator (same as yours) produced 14.7V originally. If yours does the same, with electronic ignition you risk engine shutdowns due to an overheated coil. I'll guaranty this: despite the 12V description there's no way its output is less than 13.8V.

Once I installed mine and measured the output for myself I replaced the internal regulator immediately down to 14.0V. There are several threads on the subject but this one explains what's going on pretty well. The discussion centers around coils but the coil input voltage is a critical factor. Since the alternator is producing when the engine is running, its output voltage is what the coil receives less any systemic voltage drop (voltage drop should be less than 3%).

[bigoledave]

Reply

Thanks for the information.

The first time I "fire it up" with the new alternator
I will have a voltmeter on it...and then go from there.

Reading about a coil for sale by Moyer:
Coil – with internal resistance
"..Ideal for both the early and late model Atomic 4, these coils are designated and labeled as “Standard 805”. We have been using them on our Exchange Engines for at least 15 years and selling them in our parts catalog for almost as long with no known failures which attests to their apparent good quality. Their primary resistance measures between 3.6 and 4.0 ohms at 70 degrees F which meets or exceeds the primary resistance requirements for Atomic 4s with conventional (points and condenser) ignition system and those with Ignitor electronic ignition systems and alternator charging rates up to 14.2 volts.”
(IGLM_05_31)
NOTE: Except for warranty exchange, this ignition item is not returnable.

I can not remember when I purchased the coil installed now and an identical spare I have..maybe I got them from Indigo?

Anyway...I will measure the coil resistance and play with the spreadsheet.
I will consider the addition of an external ballast resistor. I am not
enthused about modifying my new alternator to reduce the max
output voltage but of course are curious as the modification you said
you did to yours.


Comment about overheating and damaging the coil:
- I had a verrry hot engine "episode" last year with a REALLY
overheated engine....and the coil still works...which is mounted
to the head. This MAY indicate the coil MAY operate fine while "hot".

-My engine runs very cool as I am raw water cooled here in the
Northwest with NO thermostat mounted. This is the way it always has
been plumbed for the 34 years I have had the boat. I purchased
a kit from Indigo to make it run hotter.....but these old adages always
make me hesitant to add all the crap to my simple boat. The huge
heat sink of the engine block must keep the coil somewhat "less hot"

1) Keep it Simple Stupid
2) If it is Not Broken.. Don't Fix It

Cheers

[ndutton]

There were several other factors besides the ignition V=IR balance that pushed my decision to replace the internal voltage regulator. My antifreeze cooling system uses electric pumps and their voltage specification is 12V +/- 20%. The alternator came with a 14.7V output which exceeded the maximum specified. I also have an electric fuel pump, refrigeration, autopilot, GPS, GPS plotter, depth instrument, VHF and so on that would be subject to the alternator output voltage when the engine was running so I felt pretty strongly all would be happier and survive much longer if I toned down the voltage.

[bigoledave]

reply

Thanks for the info....

Ok...I am curious of course. If you felt like a writing post showing how
you adjusted the voltage that would be interesting. It is very
hard (lots of amps!) to charge a lead acid battery of any decent size to mid 14 voltsis it not? That would require a pretty high current level to do that. I always
run with my two batteries "on" so "forcing" their voltages that high
is even harder. (My two cents.)

Cheers