OMC temperature sensor instalation

[Cruisers460]

Hi, I have a mid to late 80's OMC 5.7 and want to put a oil and temperature alarm on it. The temp sensor for the gauge is located on the starboard front of the engine, does anyone know where an alternative mounting position would be? I'd like to keep the gauge as well as install the alarm!

 

[HT32BSX115]

Re: OMC temperature sensor instalation

Howdy,

Welcome Aboard!


I would put the high-temp switch in the t-stat housing where the outlet is. (engine side of the t-stat...that should be the hottest point.

The oil press switch can go anyplace in the pressurized system.


Regards,


Rick

 

[Howard Sterndrive]

Re: OMC temperature sensor instalation

the 350 in my 73 Chevelle has the 150F temp switch that turns on the cabin blower fan in the rear of the passenger side cylinder head. There's a coolant cavity/plug right at the top outside corner.... not sure if the threads/port is the same size as the one in the intake manifold. also not sure how close your omc manifolds come to that port.

I'm about to do the same investigation on my V6 Mercruiser because I just bought the Sierra alarm kit too.

 

[Cruisers460]

Re: OMC temperature sensor instalation

I would put the high-temp switch in the t-stat housing where the outlet is. (engine side of the t-stat...that should be the hottest point.

I'm not finding any ports on the heads to install it so this may be what I have to do. On the front of the OMC thermostat housing there are two large screws, one appears to be about the right size. Is this where you are referring too?

 

[HT32BSX115]

Re: OMC temperature sensor instalation

I'm not finding any ports on the heads to install it so this may be what I have to do. On the front of the OMC thermostat housing there are two large screws, one appears to be about the right size. Is this where you are referring too?

Yeah. That's where Mercruiser puts them.

I like the idea of putting a sensor in the head because it would presumably be the hottest point (a tad hotter than the t-stat housing maybe since it's closer to the actual heat generator!!!)

But it's just easier to put them in the housing............some heads don't have a place to put a sender........you're only looking for a MAX temp that will turn on the idiot light and/or turn on a buzzer.

As an aside, Mercury did a lot of alarm systems all hooked together. I.E. the over-temp, low-oil press and drive lube(low) sensors were connected to 1 wire that went to 1 buzzer and 1 light.

If the system activated, you were left with figuring out what the problem is........ high temp, low oil press or low drive oil.......... or a shorted wire (or shorted sensor) on the engine.

All the switches do is "go to ground" when they activate.....

I am going to do mine a little different.

I'll get simple Radio Shack piezoelectric buzzers (maybe one for each circuit) and a light for each one too. That way when the oil pressure is low, (only) the oil pressure low light will illuminate and (only) the oil pressure "buzzer" will activate etc....

In reality, if you put the idiot lights where you can see them easily, you could get away with only 1 buzzer for the oil pressure. You would probably see the light for the temp or drive oil etc. You'll hear a 108db buzzer any time it comes on. There's other choices of buzzers too.

Food for thought.......


Rick