Question on correct temperature for carb'ed Mercruiser 5.7

[pachanga27]

Looking through some post I read an interesting note - " If your MPI engines do not reach a minimum of 160 they will always run rich."

That being noted - for a 1989 Mercruiser 350 Mag engine that is carb'ed - what is the temperature that it needs to be at for an optimal mixture? - not rich, not lean.

I would believe 145 degrees - however - just wondering.

 

[Scott Danforth]

My 2002 carb'd had a 160 in it. However many run the 140

 

[garbageguy]

My 1998 (or so) carb'd 5.7 runs at about 160 degF

 

[pachanga27]

FYI- - both engines stay at 145 degrees at low speed (idle - as in no wake zones) and regular speed - reason I figured 145 was the norm for carb'd engines. And the engines run great - cold or warm. That post just caught my eye... as to 160 has to be there for a MPI motor to run correct.

 

[Fun Times]

If your MPI engines do not reach a minimum of 160 they will always run rich.

I've noticed in the past that the magic number for the engines (carb or MPI) that run a 160 degree thermostat seems to be 154 degrees. At 154* is when you'll notice the engine hits its optimal idle speed on the TKS or MPI engine models. Other Mercruiser engine models also have had thermostats in the 140 - 143 degree range, so it should be safe to say the high 130's to low 140's would probably be their optimal range for best efficiency.

 

[JustJason]

Mercruiser uses all sorts of different thermostat housings. Some with check balls in them, some with spacers that locate the tstat in a specific location. The best thermostat to run in your particular engine is the one that the EPC says to run when you look it up by serial number.

 

[Volphin]

Let's keep in mind that the T-stat does not dictate the operating temp of the engine. It simply dictates when it is rated to fully OPEN. Engine operating temp is going to be much higher.

 

[midcarolina]

Let's keep in mind that the T-stat does not dictate the operating temp of the engine. It simply dictates when it is rated to fully OPEN. Engine operating temp is going to be much higher.

The thermostat controls the minimum engine operating temperature and controls the flow rate through the engine to allow the cooling liquid adequate time to absorb as much heat as possible..

In many area's of the world if you remove the t-stat the engine would NEVER rise to the minimum operating temperature.