designing a overheat signal for gm 350 5.7 v8

[digitalman]

I have read multiple places its best to have a signal horn or other loud device to get captains attention when engive overheat condition arises..from something sucked into the intake, or other failures. My 5.7 gm does not seem to have it.

I know the basic circuit would be 12v to buzzer/signal to coolant sensor in block..grounding of sensor gives the horn/signal. Question is what to use as the sensor? What would be the appropriate device..basically open until overheat occurs and then a closed condition then..more or less like an idiot light in a car..but attached to a signal horn instead of a light.

Thanks! This is a great site and thanks for the expert advice and opinions.

 

[WillyBWright]

Re: designing a overheat signal for gm 350 5.7 v8

Any MerCruiser that says 5.7L should already have it. Older versions that indicate horsepower instead might not. Any 5.7 should have both a temp sender and overheat sensor already installed in the thermostat housing. The small one is the temp sender, the large one is the overheat sensor. I find that the vast majority of those that don't work are because somebody put an automotive thermostat gasket in there. Marine thermostat gaskets have a couple of small rivets in them to maintain a ground connection between the housing and the block. Most boats with a 5.7 already have alarms, usually under the dash. But again, older ones that didn't go by the 5.7 designation might not.

 

[Coors]

Re: designing a overheat signal for gm 350 5.7 v8

Go to napa and get a normally open switch.

 

[whywhyzed]

Re: designing a overheat signal for gm 350 5.7 v8

Go to napa and get a normally open switch.

yep - make sure you say switch and not sensor.
you want a switch that closes around 210F