88' Mercruiser 7.4 water temp sender question??

[NateZ]

I have twin Mercruiser 7.4's on my boat, one water temp gauge is giving some funky reading so I want to replace the sender. My motors have two water temp senders, one on the intake manifold starboard of the thermo housing, and one actually screwed into the back of the thermostat housing. (My boat does not have a temp alarm that i am aware of, maybe it was disabled prior to me getting the boat if thats what it is. I think the one in the intake manifold is the one i need to replace correct?

Side note, the motor also has a oil temp sender on it i believe right next to the oil pressure sender. I have no oil temp gauge, whats it for? Another possibly disabled alarm??

Thanks,
Nate

 

[HT32BSX115]

Re: 88' Mercruiser 7.4 water temp sender question??

one water temp gauge is giving some funky reading so I want to replace the sender

Howdy,


Temp senders don't fail all that often.......It's more likely a poor connection.........either the sender wire or ground connection between the sender & housing.

The other "senders" are actually temp or oil pressure switches. They "go-to-ground" at predetermined temps or pressures to sound the high-temp or low oil alarm.

Since they go to ground, they're frequently connected to the same wire for 1 buzzer.

Problem is, when the buzzer goes off, you're left with trying to determine which engine has low oil press or high temp..... (or which switch has malfunctioned, or the wire is shorting out someplace when oil press/temp is perfectly normal!!)


If you're getting a "funky" reading, check the gage, sender, and ground connections before you replace the sender..... That's usually the problem.


Cheers,


Rick