Two temp sending units?

[mkulin]

I have 1981 Wellcraft that has been repowered at some point in its life.

I have two temp sending units. One in the intake manifold water jacket and one in the left hand cylinder head. The one in the manifold goes to the gauge the other one goes to an audible under dash alarm is this correct? does not seem right, how does an old boat know whats too hot? Seems they are completely different types and now that I have the engine running and warmed up the audible alarm is buzzing constantly. I have good oil pressure and temp doesn't get over 180 with a cuff on.

 

[bruceb58]

Yes...some engines have those. The second one that goes to the alarm is actually a switch and not a variable resistor like the one going to the gauge.If it has one for the temp, it likely has another one for oil pressure. Take the wire off the temp switch and see if the alarm quiets. If it doesn't, look for the oil pressure switch and do the same.

 

[mkulin]

cool next someone has changed the temp gauge it is different than the rest are the sending units (manifold) matched to these gauges? And if I want to replace the temp alarm sender where do I get one?

 

[GA_Boater]

We need to know what you're working on.

BTW - 180 is too hot.

 

[mkulin]

Chevy 350 5.7 l 260HP probably from a car or truck at some point. Why is 180 too hot? Thats where all my cars run.

 

[GA_Boater]

The thermostat is a 143 degree stat, it shouldn't be 180, more like 150-160 max. Boats don't run as hot as a car.

Maybe the alarm is because the temp sensor has tripped. Has the impeller been changed lately?

 

[GA_Boater]

Also is this a Mercruiser, Volvo-Penta, OMC, etc.?

 

[mkulin]

Mercruiser going to remove the thermostat and run again. Picked up a new pump kit and will install. Then reinstall a thermostat. Can I use an auto thermo? Maybe a 180 auto thermo in there?

 

[hemi rt]

The temp sensor in the head usually goes to a gauge, the one in the manifold would be used by a PCM if the engine is out of a car. Try switching the wires on the 2 sensors and see what happens.

 

[mkulin]

Would a thermostat installed upside down effect cooling? The shizz I find on this boat. Impeller shooting cold water on the temp pellet would be a likely culprit. Old style housing X type no sleeve and thermostat can go in either way. I also drilled two 1/8 inch weep holes in the thermostat so it could always get some fresh water no matter what just take longer to heat up.

 

[GA_Boater]

Pellet always is down toward the block.

 

[mkulin]

Ok so I tested the thermostat (works fine 140 degree) put it in the right way, tested the gauge to ground works fine, engine runs great, then about 5mins in the gauge gets to 150 and the alarm goes off (90 degree day with no cover so the engine is scorching hot to the touch when stone cold). I pulled the temp switch wire and alarm is off. What temp are those $80.00 alarm switches set to go off?.

 

[mkulin]

I'm guessing exhaust manifold blocked on port side.

 

[mkulin]

Resolved. Removed port manifold and riser, backflushed and ran a coat hanger thru, clr over night and now runs cool as a cucumber