what temp should eng run?

[rknrollo]

I'm new to boats but my 5.8 cobra seems to run around 120 degs, it did get to almost 140 at very low speed, air temp was about 95 and water temp was 73 degs, I'm thinking it should run warmer than that, does this mean my thermostat is stuck open?

 

[HT32BSX115]

Re: what temp should eng run?

You might have to consult an OEM service manual to find the right temp for your thermostat.

They're usually 140* for raw water cooled engines.

Before you assume you have a problem though, check your temp with a different gage. A cheapie Harbor Freight Infrared temp measuring device works well.


Here's the one I have.....just point it at the t-stat housing...

 

[rknrollo]

Re: what temp should eng run?

I have an infered thermo, I will check it, why do boats run so cool? I know very much about cars and too low temps and high rpms create wear and with efi it will run rich until up to temp. I will check it. maybe I will pull the sensor and try one of my mech gauges.

 

[dubs283]

Re: what temp should eng run?

why do boats run so cool?

on raw water cooled engines, the cooling system isn't pressurized like on an auto - which tend to run in the 210 degree F range

also, there are not nearly the amount of emmisions restrictions on marine engines, hence you do not need the higher running temps to maintain a "cleaner" fuel burn

there is a need on marine engines to run at sustained higher rpms than on autos, cooler temps allow for less chance for severe internal engine damage

 

[HT32BSX115]

Re: what temp should eng run?

on raw water cooled engines, the cooling system isn't pressurized like on an auto - which tend to run in the 210 degree F range

also, there are not nearly the amount of emmisions restrictions on marine engines, hence you do not need the higher running temps to maintain a "cleaner" fuel burn

there is a need on marine engines to run at sustained higher rpms than on autos, cooler temps allow for less chance for severe internal engine damage

Um....the above is not exactly true.......



Raw water cooled marine engines are designed to operate in salt water.

If you run at temps higher than about 140-150, the salt and other minerals tend to precipitate out of solution and "collect" inside the engine etc......

If the engine is closed cooled it can run at much higher temps.(where it will run much more efficiently)

A 140 degree t-stat is common for a raw water cooled engine.

I have a 160 stat in my (closed cooled) 454 and the gage runs at around 170-180.

Cooler temps have nothing to do with engine damage from running at high power settings and in fact, an engine running at higher temps will have better compression and better combustion and use less oil.

It's also VERY important that you use the correct temp t-stat for your EFI engine or the ECM will think the engine is cold all the time and try to run it rich while "warming up" It's designed to operate at the temp specified in the OEM OMC service manual (that's why you need to get one if you do not have one.) Don't use a Seloc or Clymer manual for other than a knee-pad ....or for starting your wood-stove!


Regards,


Rick