Problem with temp guage or sending unit.

[David Arnold]

I used the boat for the first time this season and noticed that the needle was pinned at 240 degrees after running for under 10 minutes.  I tested the thermostat on stove and it opens so no problem there.  Left the boat overnight and when I checked the temp in the am before starting the engine the gauge was at 150.  Within 2 minutes of starting the engine the needle is once again pegged at 240.  Clearly I don't have a problem with the engine but with either the gauge or sending unit.  From what I have described above any ideas which one is the culprit?

[Stu Jackson]

Have you burped the engine?

[David Arnold]

What is "burping" the engine?  I just started it as usual for the first time and it started right up.  The engine sounds right and certainly seems to be running at the correct temp.  All is well except what the gauge is telling me.

[Ken Juul]

Burping refers to getting all the air out of the system, especially the loop to the water heater.  If there is air in the system it will migrate to the thermostat housing as steam, quickly showing a high temp.  Do you also have a high temp alarm?  If yes, was it going off? I'm sure there is way to test the sender with a multimeter, but I don't have the specs.  Maybe call/email Joe Joyce at Westerbeake, he has been very helpful sorting out stange engine problems in the past.

[prh77]

If you are indicating 150 before you start the engine, you have an indication problem. Check and clean all wiring connections, as high resistance will cause high readings. Also verify the sending unit is properly grounded.

[Stu Jackson]

What is "burping" the engine?  

Burping the engine is an old Scottish myth that is raised every spring when people start their engines for the first time and the temperature goes through the roof.  It is usually accompanied by a change in antifreeze.  Or the hoses to the hot water heater (http://c34.org/bbs/index.php/topic,3769.0.html)

You can read all about BURPING in Reply #6, here: http://c34.org/bbs/index.php/topic,4518.0.html

You can also find it by doing a search on "burp!"

[Ron Hill]

Peyton : David's gage is probably OK, as the needle remains at it's last reading until the power (key stitch) is turned ON.  Then the temp needle will drop below 100 degrees. 

[prh77]

Ron; I was assuming the gauge read 150 when the key was turned on and the engine was cold. Yes, you are correct, the system does remember the last temp. I guess you have been doing this for awhile.

[David Arnold]

Just to clarify a couple of points:  First, the gauge goes down to zero or lowest temp when the key is turned off.  It's only when I turned the key on that the gauge immediately shot up to 150.  From there it quickly went up to 240, the max reading.  At no point did the alarm sound and in fact when I checked the engine after it had been running for a while it was clear that the actual engine temp was in the normal range.  From what I gather the most likely culprit is a bad ground either at the sending unit or at the gauge itself.  I will check all connections next weekend.

[canuck]

For peace of mind, I carry an infrared thermometer.

[Ron Hill]

David : Sounds to me like you have a temp gage problem, if the engine is cold and the gage jumps up to 150 when the key is turned ON.