Exhaust Temp sensor 3889526 Spec?

[xixp]

Hi ,
I have a 2012 V8-300 CE A that runs at normal temperature at planning speed (174 degrees) but when it goes down to idling the Exhaust temperature alarm goes off .
This engine has a closed loop system ; Ive had the Heat Exchanger cleaned , thermostat replaced, new circulating pump and raw water pump.
Per the online diagram it seems that this particular engine runs coolant through the manifolds and raw water is directed to the elbows so the manifolds should be in good shape. (boat has 170 hours mostly used in fresh water; only two years in salt water).

Ive checked the manifolds temperature with an IR gun and it is around 200 F at idling which seems high but I know that CAT engines run hotter.
Therefore I wonder if somebody knows the trigger temperature of the manifold sensors used in this particular engine to rule out a possible sensor problem.

TIA!!

 

[alldodge]

Don't know to much about the VP CAT cooling system, but Merc uses what's called pop-it valves in the raw water side. The valves cause lost of issues for Merc. Does your motor have something like that?

 

[xixp]

Some variations of this engine have 2 extra thermostats for the exhaust elbows but not this one. Raw water is routed to the elbows after going through the heat exchanger. Manifolds are cooled by the closed loop circuit ; coolant goes from the cold side of the HE, circulator pump, engine block, manifolds and hot side of the HE.

 

[alldodge]

Get a short piece of clear hose, double barbed fitting and couple of clamps from a hardware store. Disconnect the hose going to the HE coming from the raw water pump and place it inline with the hose.

Then run the motor to see if you see air bubbles

 

[Nashville]

Hi ,
I have a 2012 V8-300 CE A that runs at normal temperature at planning speed (174 degrees) but when it goes down to idling the Exhaust temperature alarm goes off .
This engine has a closed loop system ; Ive had the Heat Exchanger cleaned , thermostat replaced, new circulating pump and raw water pump.
Per the online diagram it seems that this particular engine runs coolant through the manifolds and raw water is directed to the elbows so the manifolds should be in good shape. (boat has 170 hours mostly used in fresh water; only two years in salt water).

Ive checked the manifolds temperature with an IR gun and it is around 200 F at idling which seems high but I know that CAT engines run hotter.
Therefore I wonder if somebody knows the trigger temperature of the manifold sensors used in this particular engine to rule out a possible sensor problem.

TIA!!

If I recall correctly:
Manifold. First stage, 190-F. Second stage, 205-F.
Riser. First stage, 210-F. Second stage, 220-F.
This motor has exhaust “thermostats”.

 

[xixp]

Thanks for the answers!

 

[Nashville]

Thanks for the answers!

No problem. Where do you boat, north or south? 174-F seems a little warm for this motor (5.7L with Cats, EGC). They tend to run low 160’s if sea water is below 80-F or so and ambient around 90-F. 174-F isn’t hot, but might be a telltale sign. Between this and the exhaust alarm, suggest checking the impeller and pump housing to be sure there’s proper flow.