MerCruiser 5.0L MPI 260 running temp question

[Kieran Long]

I hope someone can help me, I have a Smartcraft-100 connected to my MerCruiser 5.0L MPI 260 but cannot figure out how to check the engine’s operating temp. I normally get a 95 to 100 degree reading from the “Engine Water Jacket Temperature” screen on the Tachometer which correlates with a temp gauge on the dashboard (this gauge needle never moves except when I kill the engine at which point it moves from at rest (100) to about 115 degrees. This gauge’s range is between 100 and 250 degrees but never moves during normal operation. , Is this the engine temperature reading?

The only other reading I get is from the “Sea Temp” reading on the Tachometer with normally sits at about 120 degrees and only moves a couple of degrees either side of the 120 mark. Not sure what to make of this, I do my boating in CT not at the equator…

I read in the engine manual that the normal operating temp should be 160 degrees but I don’t know how to monitor it. I cannot find any reading of 160 degrees.

I’d appreciate any help It nerve racking running the engine not knowing if it’s running hot or not.

Thanks in advance,
Kieran

 

[Half Fast]

The "temp" gauge you are referring to on your dash should be reading somewhere between 160-180. 100-110 means you have some faulty wiring or a bad sensor or something. Is the temp gauge in the dash a SC gauge as well?

You can always borrow an infrared temp sensor from someone and point it at your manifolds/risers and see what it says (will probably still be a bit lower though than the temp inside) - but you definitely want to fix the problem so you get an accurate reading from SC - especially in case you run into a problem that causes your temp to spike.

Good luck.

 

[Kieran Long]

Thanks for the quick reply. Yes the other gauge is SC. So I take it it’s either a bad sensor or a bad sender right? Is there any way of determining which? I do get a reading of 95 or so.
Thanks,
Kieran

 

[Kieran Long]

Half fast, thanks for the info.

Is it ok to test the gauge & wire by pulling the wire off the sender sensor and grounding it. I read on other posts that if I ground the connection, the gauge should “red line” will this damage the Smartcraft system

 

[Ididntdoit]

Could a PO have removed the thrmostat?

 

[Half Fast]

Half fast, thanks for the info.

Is it ok to test the gauge & wire by pulling the wire off the sender sensor and grounding it. I read on other posts that if I ground the connection, the gauge should “red line” will this damage the Smartcraft system

I wouldn't want to speculate as to whether you'd blow it or not - I'm not familiar enough with it to offer that level of advice I'll just tell you that my 99 270 was repowered with a 6.2MPI that had smartcraft, but it was hooked up to the original guages. I bought a GPS with digital smartcraft guages built in and decided I was going to wire it up myself. I must have connected, disconnected, grounded, crossed, and otherwise mis-plugged the smartcraft cabling 100 times over the course of a month before I finally got it working - so at least in my limited experience, it was fairly forgiving.

Good Luck!

 

[Kieran Long]

Guys, thank you, I'll give it a go.

Cheers,
Kieran