Water Temp Gauge

[72INVADER90HP]

Is there a way to hook a Temp gauge to the 1/4 inch plug hole on the top of the head of a 1975 chrysler 90 hp?

 

[Frank Acampora]

Re: Water Temp Gauge

You buy the gauge and sender right here at iboats or online or at your local marina--whatever suits you. The gauge should come with a "sender" which screws right into the 1/8 inch NPT hole in the top of the head. If you already have the gauge, then you need to buy the sender only--they do sell them separately but they are a little pricey.

The most difficult thing to do will be to get the stainless plug out of the hole. Believe me, they are in there tight. A little bit of corrosion and they are damn near permanent. A little bit of heat and an impact screwdriver are a big help. coat the threads of the sender with anti-seize or teflon tape before screwing it in. These are tapered threads so don't get too happy with the wrench. Just screw it in tight enough to stop leaks.

If you already have a hole in the dash and the stainless plug removed, then the installation is about 10 minutes. Probably take an hour to remove the stainless plug though.

 

[Frank Acampora]

Re: Water Temp Gauge

Forgot to add that Orange wire is either overheat indicator OR temperature gauge wire. NOT both. If you want to keep the overheat indicator then you need to run a separate wire for the gauge. "Sender" is a variable resistor--less resistance when hot. Power goes from dash to gauge and orange goes fron gauge to sender. As sender heats up, more voltage will pass through it to ground, thus more voltage will pass through the gauge and the meter will read higher.

And if you absolutely can not get out the stainless plug, you can drill and tap the boss in the top of the block right behind it.

 

[72INVADER90HP]

Re: Water Temp Gauge

Thanks. I do not have an over heat buzzer on the engine, I trust the water temp gauge better. Now anouther ? My Chrysler has a distributor and I hook one of those old time tach and dwell meters to it to check the RPM's since the meter has a 6 and 8 cyl on it I use the 6 cly switch and and divide the number in 1/2 because I have a 3 cyl. Cam I buy a regular tach that is made for 3 cyl or do I have to go with a specail tach?

 

[Frank Acampora]

Re: Water Temp Gauge

If your distributor has points, it should work as you described because points are 12 volt powered. Points distributor will have only one white wire on the insulated terminal on the side. If it is electronic, (two terminals, two wires) the electric eye is powered by 12 volts constant on the blue wire. I'm not sure what the voltage on the white wire is but it would be intermittant like points so the tach might work from this source.
Fot your info: The constant 12 volts powers a diode. The light beam is broken by three shutters on the distributor shaft This alternately energises and blocks a photocell that the white wire is connected to.

You have a 12 pole alternator so you have a choice of tachs. The Teleflex and most other brands regular tach works on this engine with the adjustment button arrow on the back of the case set to the "3" position. The white wire from the CD box is the signal source for the tach.
Force engines use a special 20 pole tach and the AC from the alternator is the tach signal.(purple wire.)
There are also tachs made (I had one but don't remember the brand) that work on 12 pole AND 20 pole alternators. Mine was set to "3" for 12 pole and "4" for 20 pole. (different 3 and 4 than the regular tach.) I think others are actually numbered 12 and 20.