Running temperature of 250 Pro XS

[Davidbassfish]

2008 Mercury 250 Pro XS Serial # 1B586111
What temperature should a 2008 Mercury pro XS run at?
I do not have a temperature gauge, but while running on muffs, it takes no time for engine cylinder walls to reach 160's on one side and 170's on the other. I am checking it with a infrared laser temp gauge. The pee stream out of the tell tail is cold as is the water coming out of the prop. From what i read the thermostats are 130??? I am not getting any alarms, when should they go off?

Thank you for the response.

[smoken86]

You would have alarms going off at 170. Checking with a infrared laser is going to give you temp of the metal in that spot and it will absorb a lot of heat. I am assuming you are checking it on the thermostat housing?

I would hook it up to a scanner if you are at all concerned and see what they are reading.

[Davidbassfish]

i was actually checking the temperature on the cylinder and heads themselves. I will run again and check the temp of the thermostat housing.

[Davidbassfish]

i measured the temperature at the thermostat housings and they were 136 and 138. the middle cylinder, (right side), outside of block temp was temp was 165 and left side was 180. Again checking with laser temp gauge.

[JOE54]

depending on surface temp at idle in the lake / tank 120ish a pristine new w/p clean system, in 40ish surface temp high 118ish this is after thermostats have cycled and engine is up to temp checked on CDS G3 for individual head temps port side will be cooler a degree or so most times , on plane this is not valid info temps will be lower regulated by poppet valve water flow control

[smoken86]

i measured the temperature at the thermostat housings and they were 136 and 138. the middle cylinder, (right side), outside of block temp was temp was 165 and left side was 180. Again checking with laser temp gauge.

136/138 on the housing you are fine as I bet it is 10 or so less on the sensor reading. Second most important thing outside of the temp is if it is cycling correctly, which you may not be able to see without being hooked up to the computer.

[EuropeanAM]

The ONLY accurate location to check temp on this engine is dead-center of the thermostat cover on each bank.

Outside of that, you're going to get temps that can be WAY off.