Adding overheat alarm

[jrbdjb]

I want to add an overheat alarm to my Mercury inline 6 115. This would be simple except I want to have the "self test" feature also. I can find lots of engine schematics showing the sensor and tan wire, but nothing beyond the powerhead. Can anyone tell me how the self test works and maybe a wiring diagram?

Thanks!

 

[alldodge]

Alarms have a 12V and ground connection. The alarm is connected to 12V when the key is turned ON. The Tan wire is grounded by the sensor switch mounted in the water jacket on the motor. To test the alarm, splice another wire to the Tan wire, thru a manual switch to ground.

 

[Faztbullet]

Motor runs too cold as design has no t-stat. It will overheat and seize before a alarm would be triggered. Better to install a water pressure gauge

 

[racerone]

^^^ with the above.-----Also install a new impeller every 2 years.---Temperature gauge is also an option.

 

[jrbdjb]

Thanks for the replies guys. I hadn't considered the lack of a thermostat. Think I'll go with a temp gauge. I generally change impellers every spring, maybe over kill but cheap insurance.

 

[Faztbullet]

Get a gauge without numbers ...like below

 

[Texasmark]

^^^ with the above.-----Also install a new impeller every 2 years.---Temperature gauge is also an option.

I just bought a 2002 rig. No idea as to the total condition of the rig and I'm not one to change out parts for the sake of it. My water pump is doing all one could ask and I'm not going to fix what isn't broken. I had a blank spot in my dash gauges and decided to install a gauge monitoring engine coolant. Most folks on here recommended a water pressure gauge, but Mercury Marine engineers install an OT switch on the engine....they are concerned about engine block temperature, not water pressure.

Well if engine temperature is what I'm interested in and autos and trucks have temp sensors, not pressure gauges, why not install a gauge indicating what really interests you.....engine temperature.

So I did and now I can watch my engine warm up, watch the thermostat open and maintain set temperature, get up on plane and watch my poppet valve open and see the engine temp drop down to about 50F above ambient water temp, slow back down and see the poppet close and the engine temperature come back up to thermostat opening temp...............all electrical connections, no water pipe to come off/leak/clog/freeze up in the winter/get pinched.............

 

[racerone]

A marine outboard / boat engine FLOATS in it's cooling water supply.-----An automotive engine carries its cooling water internally.-----The outboard benefits from a pressure gauge to monitor pump condition.

 

[Faztbullet]

I suggest all motors have a pressure gauge do to the fact you can monitor condition of impeller, see when its starts to wear as pressure drops, instantaneous result if you run into trash....hard to tell from a "P" indicator you had a pressure drop as its a restricted orifice.

 

[Texasmark]

I suggest all motors have a pressure gauge do to the fact you can monitor condition of impeller, see when its starts to wear as pressure drops, instantaneous result if you run into trash....hard to tell from a "P" indicator you had a pressure drop as its a restricted orifice.

Good point and you surely would know. For pump condition, I am using the tell tale at idle. Thanks for answering that question.

 

[Faztbullet]

For pump condition, I am using the tell tale at idle.​

So you can tell by looks if you had a 5psi drop???

 

[Texasmark]

So you can tell by looks if you had a 5psi drop???

No. Seemingly good enough for my run for that day. I have been thinking about it this morning and in my little world of boating, I am no more than a few miles at most, usually a mile or so max, from my launching point in protected lakes. Running off shore 20 miles, for an example, would surely be a different story. I see your point. Thanks.

 

[jrbdjb]

Thanks for all the replies. Interested in the pressure gauge idea. How many psi should an inline 6 have?

 

[Faztbullet]

You need a 0-15 psi...you will see and 1-2 psi at idle and 8-10psi at WOT

 

[jrbdjb]

Thanks again for the info everyone!