thremostat ???

[mike456]

1992 Mercuiser 5.7L S/N OD70904 new owner. I pulled a 142 degree t-stat when winterising her last year. Took it to a parts place to get a new one and the guy told me that engine requires a 160 degree which I purchased and installed. I'm working on outdrive and bellows now so I have not starter her yet. I'm still confussed as to why I need 160 rather than 142. Wouldn't running cooler be better??

 

[Don S]

Re: thremostat ???

Well, your serial number is missing one of the numbers, so it doesn't help much that way.<br />Normally, the 142° thermostats are for raw water cooled engines, and the 160° is for closed cooled engines. Which do you have??????<br />Also, running warmer is actually more fuel effecient and better for the engine than cooler to a point. In brackish or salt water, the higher temps will bake on the salt and minerals inside the cooling passages.

 

[Laddies]

Re: thremostat ???

The book calls for a 160 degree stat some one must have change it to a 142 at a earlier time a little more temp may help idle some what if you want to run a colder one run it

 

[Don S]

Re: thremostat ???

Not sure what book you are looking at Laddie, but according to the Merc parts catalog, depending on his SN and what design (1,2,or 3) cooling system he has, he could have either a 140 or a 160.

 

[mike456]

Re: thremostat ???

Don. S/N is OD709044 I have a raw water system and run mostly in fresh/brackish and salt water for summer months only (NH location). Do you think I should switch back to 143?

 

[Laddies]

Re: thremostat ???

That was a Mercruiser Manual Don, 5.7 liter serial number OB-525982 to OF-600999 - 1988 to 1995 for design 2 and 3 thats why I told him he could run either. Sorry if I offended you just trying to help someone out--Bob

 

[mike456]

Re: thremostat ???

So how can I tell if I have design 1,2 or 3 and therefore which stat to run? As noted it's a raw water system.<br /><br />This stuff can get very confusing and we are all happy to get and give advice. I don't think anyone is offended. Thanks for all the help.