Mercury 115 Thermostat & Temp Sensor

[SpikeJ]

I have a Inline 6 115HP Mercury with an eletric type themostat and temp sensor. My understanding is that the temp sensor is used to send a signal to the gauge on the dash it was not hooked up when i connected it I still had no reading. It looks like the sensor should have a varing resistance with the temperature change. Any info on the range of the sensor how would I determine if it is the gauge or the sensor? Does not seem to be very complicated. What does the thermostat do?? Looking through the Selocc manual indicates that it is related to the cooling but how?

 

[Chris1956]

Re: Mercury 115 Thermostat & Temp Sensor

Spike, I do not know of any inline 6 115HP Mercs that have a thermostat. I think the later models had a temp sensor and buzzer. These sound when the motor overheats. You migh test it in a pan on the stove. It should short to ground at 175-200*F.

What is the year of that motor? You may look up the year by serial number at maxrules.com

 

[SpikeJ]

Re: Mercury 115 Thermostat & Temp Sensor

So then does the Gauge only have two positions cold or hot. I'm thinking that it should move somewhere between hot and cold during normal operationg range and give you a full ground when it is in a overheat condition. That being the case the sensor should have a varying resistance to give you the different ranges which should modulate the gauge. Does anyone know what the varying resitance readings would be?? As for the year that has been an interesting saga. I have never been able to find a serial number. I know they tell me to look at right side motor mount but their is no plate the best I can tell from located matching carburators, trim systems, wiring etc. it is 1986 to 1988. Best I can come up with if anyone has any other hints at how to date the engine I would be thankfull.

 

[Chris1956]

Re: Mercury 115 Thermostat & Temp Sensor

SpikeJ, There are two types of temp senders. One for a variable resistance for use with a gauge. The other is open or shorted to ground for use with an idiot light in autos, or a buzzer on OBs. These same types of senders are avail for Oil pressure gauges and idiot lights for autos and I/Os as well.

It is likely your sender is for the buzzer-type alarm.

BTW - Merc had one sensor of each type on their V motors.

See if there is a plug on the powerhead with a serial number. Second choice is to look on the block (starboard side 1/2 way up) for a part number, that you can match up.

 

[SpikeJ]

Re: Mercury 115 Thermostat & Temp Sensor

I believe I have the variable resitance type. With an ohm meter I am reading some resistance. My questions is what the resistance range should be for the sensor. If I have the 2 types I should wire the thermosat type to a buzzer-type alarm which would simply give me a short to ground on high temp?? Thanks for the engine Id hint I will check the block number. Where would the plug be??

 

[Chris1956]

Re: Mercury 115 Thermostat & Temp Sensor

I am not sure the IL6 will have the serial number on a welch plug, but you never know...
The variable resistance types have prescribed range. Maybe the manufacturer's web site will give you the values.