Tach and temp switch

[brokenwrist]

Hey guys, My tach took mondo dump over last winter and I have been trying to find a replacement for a 3 cylinder engine with little to no luck ( at least something I can afford anyway) that will fit in the factory hole. Would any one of ya'll happen to have a chrysler tach laying around that works, I can hook a 4 cyl tach up and it registers but Im fairly certain it's not accurate. Secondly since I bought my boat a couple years ago, the temp gauge has never worked, the previous previous owner had some jerry rigged wiring coming off the rectifier. I resolved that mess, I have 12volts coming into the gauge, but nothing on ground side. I can ground out the switch wire and the gauge will move full sweep. So that tells me that my temp switch in the head is caput, and probably has been for some time. Is the switch something I can just go to the parts store and pickup, as long as its the same thread size and pitch?

 

[Nordin]

If you get a Chrysler tach there is a switch at the back of it where you set if it is a 2,3 or 4 cyl. engine.
If you use another tach you have to know how many poles the alternator under the flywheel has.
Older 3 cylinder Chrysler used a 20 pole typ.

The factory temp sensor mounted in the head is not a sender to use with a gauge.
It is a termoswitch off/on typ which grounds out the circuit.
It is supposed to be connected to a buzzer/horn or a light.

If you connect it to a gauge the gauge will only show zero or full sweep because the termpswicht only has off and on position.

 

[jerryjerry05]

A pic of the back of the tach you now have?
A pic of the temp sending unit on the head?

If someone's installed a gauge ? then the sender might be in a different place.
Top of the head is there anything there? Pic?

Caput sender, you need to remove it and keep it hooked up and drop it in some very hot water and see if the gauge works then.
Motor needs to be hot for it to work??

 

[kbh121956]

Brokenwrist - There are a few 20 pole tachometers on eBay. Do a search for "Chrysler outboard 20 pole tachometer" it will bring them up. I think that you would have a 20 pole alternator, if I'm wrong these guys will let you know.

 

[jerryjerry05]

Nope your probably right.
They used the same stator up until they changed to Mercury in some 91 models.

 

[brokenwrist]

original chrysler tach, selectable for 2, 3 ,and 4 cylinder engines. My dash has the hole where the buzzer should have been but, I have a temp gauge instead. I have tried removing the sender, keeping it hooked up, and hitting it with a torch. Gauge never moved, even tried running a ground jumper and heating it, to no avail. It just reads zero all the time. Engine dumps warm water out the ports. The sender I speak of is threaded into the top of the cylinder head, and the other location next to the thermostat has a plug in it. I'll do a search for the tach on ebay. Again thank you for the help guys. I really want to get my engine running tits, before fishing season opens this year.

 

[jerryjerry05]

Maybe someone has unhooked the alarm?
The alarm could be in the shifter housing?
To test the alarm and gauge.
Ground the orange lead on the connection bar.
Ground the sending unit, heating the parts might not work but can destroy the contacts in them.

 

[brokenwrist]

alarm is long missing. replaced with a chrysler temp gauge. I've disconnected the lead from the switch it's hooked up to, and grounded it before. The gauge moves full sweep. So I know I have good connection. This is what leads me to believe that the sensor is dead. I know it's like a 3/8 thread pitch, so would automotive sensor work?

 

[jerryjerry05]

Yes an automotive would work.
BUT?? what one??

Most auto senders are way bigger and won't fit.
Maybe try Grainger, sometimes they can get something to work?
E-bay "chrysler outboard temperature sensor" they have a couple.
One of them looks like it might be for a sweep gauge???

 

[Redbarron%%]

I added a resistance sensor to my Force in the hole that the old flush hose attached on my Sport Jet.
Later I found the sender that bolts under a head bolt and reads the surface temp of the head cover as original on my Hobie Jet Skiff.
Both worked OK, but using the surface sensor let me put the flush hose back on.
The horn was not use originally on my boat and was not installed, but I added one using the temp switch that was there on the head and a Radio Shack pulsing Pizeo Buzzer in the console.
It is handy to have both. If you have the oil injection you must have the horn for low oil alarm as well. My system is premix so that is not necessary.
Both are the answer.
If you want to order a 1/8" sender Amazon has them listed, but you need to know the proper resistance range of your gauge. I was lucky as the one I blindly ordered worked and was correct.
You can test it by running extension wires from ground to the body of the sensor and the terminal so that you can drop the sensor in to a beer can with the top cut off half filled with water and boil it with a propane torch and the gauge should read ~210 *F.
This test will assure that the gauge is reading right to protect your engine.

 

[brokenwrist]

update. After several diagnostic tests, I have determined that my tach head is dead. I essentially gave up on the temp gauge. I found really nice looking faria euro gauges that look similar to my oe gauges, and aren't all that expensive, will fit in my current openings, and the temp gauge comes with the proper sized sender. Thanks guys for all your help.

 

[jerryjerry05]

Make sure the tach is the right one.
Might be a 12pole?

 

[brokenwrist]

works with all 12 pole alternators

 

[jerryjerry05]

Take some pics of the installation.
I'd like to see how they look?

 

[brokenwrist]

might be a little bit before I can get the new gauges bought. Wife had to make a trip the er this past friday, and they did a ct, blood workup, 2 bags of saline, and 2 different iv antibiotics. I'm afraid to see the bill.

 

[jerryjerry05]

Hope she's OK!!

Since I hit 65(oh my) my health hasn't been the best
One thing I did was get supplemental insurance coverage.
That saved me from THOUSANDS of $$$ on bills I wouldn't be able to afford.
I'm going in next week for heart catherazation,
No way could I afford my %

 

[brokenwrist]

shes much better now and healing nicely. hope all goes well for you.

 

[BarryK3]

Previous owner had replaced the tach in my dash with a 12 pole and my engine needs a 20 pole. RPM reading was too high. I was able to get it reading correctly by adding a resister to the board.

 

[BarryK3]

Here is where I got the idea. I was able to just add one resister in parallel to lower overall resistance. Then I was able to use the adjustment screws on the back of the Faria tach to dial in the correct rpm. It is hard to find a 20 pole tach to match the other gauges so I decided to modify the existing one which did match except for the 12 pole problem.

 

[BarryK3]

More Faria tach info: "Faria no longer makes a 20 pole tach".