140 or 160 Thermostat 5.7

[UtahBoating]

1992 5.7 mercruiser. Winterized the boat today and when I pulled the thermostat it is pretty corroded and I bent it good getting it out. Going to replace it with all the gaskets. There is a lot of info out there and I can't pin point which one I need. The old one I took out is too corroded to see what it was. This is a fresh water boat. I have seen several posts that say 140 is standard but others say 160 is used in fresh water boats. Also if anyone has any recommendations on a complete kit I can buy I am open ears.

Thanks for the assistance.

 

[Fun Times]

Hi there, it will depend on what thermostat housing design you have to what thermostat temp you should be using. Below are the three options for 1992.

STANDARD COOLING SYSTEM(DESIGN I)

STANDARD COOLING SYSTEM(DESIGN II)

STANDARD COOLING SYSTEM(DESIGN III - ALPHA)

 

[UtahBoating]

I have the design II housing. If I go to mercury marine and put my serial number in, it still shows the 140 and 160 available for the design II.

 

[thumpar]

Mine is a little different but closest to design II in function. I run a 160 degree. Mine only runs in freshwater. The temp gauge never goes a tick over 170.

 

[UtahBoating]

I cleaned up the old thermostat and found it says v142. I am assuming this is a 142* thermostat. That is what I will replace it with. Does this sound correct?

 

[JoLin]

I cleaned up the old thermostat and found it says v142. I am assuming this is a 142* thermostat. That is what I will replace it with. Does this sound correct?

You'll be fine. My starboard (1992) engine was replaced in 2003 with a rebuilt block and Vortec heads, but they retained all of the old cooling system, When I replaced all the hoses and t-stat last year I went with a 160, just so I'd get the same temp readings I get on my port engine, a 2013 Quicksilver complete replacement engine. Merc specifies 160 for that one.

Relax, You won't go wrong replacing your 142 with another in the same range.

 

[UtahBoating]

You'll be fine. My starboard (1992) engine was replaced in 2003 with a rebuilt block and Vortec heads, but they retained all of the old cooling system, When I replaced all the hoses and t-stat last year I went with a 160, just so I'd get the same temp readings I get on my port engine, a 2013 Quicksilver complete replacement engine. Merc specifies 160 for that one.

Relax, You won't go wrong replacing your 142 with another in the same range.

Thank you for the follow up. I can now have piece of mind I ordered one that will work.

 

[Fun Times]

If I go to mercury marine and put my serial number in, it still shows the 140 and 160 available for the design II.

The 160 on the design II is for special emissions made only for the Bodensee Germany area....AKA Lake Constance. http://www.bing.com/search?q=bodense...D773&FORM=QBRE

The emissions for that lake are pretty tough that the engine manufacturers had to set up a different system to meet the requirements. In the following link is just some of the part for the emissions kit... plus there's a few other things needed on certain engine models and you have to watch the "notes" for the word Bodensee.
https://www.perfprotech.com/mercruis...embly/1014/490

As long as the 160 degree seem to fit good and you were able to use the same O-ring design as you should have had below the T/stat then you shouldn't have any issues running the 160 but the correct one recommended by Mercruiser is the 140 and in "some" cases incorrect fitment can cause engine temperature fluctuation seen on the gauge.