Thermostat Temps for 4.3 ltr Merc V6... 140 or 160?

[badcarma58]

I have twin 1987 4.3 liter V6 Mercruiser 205 262 CID on my 270 Sundancer.

I just purchased this boat last year, and I have been trying to obtain as much literature as possible, just in case I may need it.

Looking through all my manuals, etc., I am getting 2 different pieces of information from various sources for the same engine.

One source says that my operating temp needs to be 140 degrees. Another source says 160 degrees. Which is it?

How can I find out what the true operating temperature should be for these motors?

 

[Bondo]

Re: Thermostat Temps for 4.3 ltr Merc V6... 140 or 160?

One source says that my operating temp needs to be 140 degrees. Another source says 160 degrees. Which is it?

Ayuh,... Raw water cooled, in Saltwater, use the 140?....
Raw water cooled in sweetwater, use the 160?....
Closed cooling, you can use a 180?....

 

[badcarma58]

Re: Thermostat Temps for 4.3 ltr Merc V6... 140 or 160?

I'm in freshwater, and currently have 160 degrees in it.

The manuals never mentioned freshwater or saltwater. One manual just said the Thermostat was 140. Another just said 160. So... I was just confused. One has to be better than the other. A mechanic I used to know always said that in boats, cooler was better on the motors.

 

[mikel1291979]

Re: Thermostat Temps for 4.3 ltr Merc V6... 140 or 160?

Your going to burn too much gas with 2 4.3's. I will help you. Take one of them out and send it to me. I won't even charge you to take it off your hands. Now you can haul more people since you lost 600lbs after losing that completely unnecessary 2nd motor.

 

[paultjohnson]

Re: Thermostat Temps for 4.3 ltr Merc V6... 140 or 160?

My merc owners manual says go w a 143 deg... my Clymer says and I quote... Whenever a Mercruiser engine equipped with a 143 deg stat is operated for long periods of time in cold water areas at very low rpms [such as when trolling] install a 160 deg stat. This improves combustion under such operating conditions,gives,smoother low speed operation,and reduces crankcase dilution caused by condensation. You should however, avoid wide-open throttle operation when using the 160 deg stat..................... For what its worth

 

[ziggy]

Re: Thermostat Temps for 4.3 ltr Merc V6... 140 or 160?

from mercruiser s/m 7. pp 1B-4. for a mcm 205/4.3LX (262cid).. thermostat. 143*F.

 

[Don S]

Re: Thermostat Temps for 4.3 ltr Merc V6... 140 or 160?

The manuals never mentioned freshwater or saltwater. One manual just said the Thermostat was 140. Another just said 160. So... I was just confused. One has to be better than the other. A mechanic I used to know always said that in boats, cooler was better on the motors.

You don't mention which manuals you looked at, but here is the page from the OEM Mercruiser manual that Ziggy referenced. I sure wouldn't put much faith in what a Seloc or Clymer aftermarket manual said.

 

[Finnerty]

Re: Thermostat Temps for 4.3 ltr Merc V6... 140 or 160?

I have the same question about my MIE 330 (closed cooling). Mercruiser Manual #3 says I need a 143 degree thermostat. When I tried to buy this at our local Mercruiser Authorized parts dealer he said "no, you need a 160 degree". Is he wrong or has the recommendation changed since 1977...? and will it make any difference? Also sold me a 13 psi pressure cap as "this is what is used now" instead of the (manual specified) 14 psi cap. Wondering....

 

[Don S]

Re: Thermostat Temps for 4.3 ltr Merc V6... 140 or 160?

http://forums.iboats.com/showthread.php?t=468283