Thermostat temp change on Merc engines?

[Texasmark]

Looking for a replacement OEM 14856 143F stat. Popular temp in Mercs. Had it in my 90 and now in a 115.

I have used Sierra for years and have had good luck with their parts. Now googling that PN, Sierra comes up with a replacement number and opening tem is 120F and listing says it's a replacement for the posted number. Any ideas

Merc online parts catalog makes no mention of opening temp for 14586.

 

[jimmbo]

120 is probably the temp where it begins to open, and is fully open at 143

 

[Texasmark]

120 is probably the temp where it begins to open, and is fully open at 143

The pellet is stamped 143 and I have tested them before on the stove with a pan of water, a string and a candy thermometer. I understand smaller engines run 120s but that was just stray hearsay I picked up on here and didn't validate it. Thanks.

 

[jimmbo]

The Stat really only controls the temp at Idle and low speeds, on your engine. At higher speeds a pressure valve opens to allow water to bypass the stat. It might be because the stats are too restrictive for the amount of water needed to keep the engine cool at higher loads/speed

 

[Texasmark]

The Stat really only controls the temp at Idle and low speeds, on your engine. At higher speeds a pressure valve opens to allow water to bypass the stat. It might be because the stats are too restrictive for the amount of water needed to keep the engine cool at higher loads/speed

Boy that was a quick answer.....it's 3:20 AM CDT here. Flopping around in the bed decided to get up make a pot of coffee and do some gabbing.

Manual says that 2500 is the opening point for the bypass saying that around that rpm is where the water pump develops enough pressure to unseat the valve. Considering how hot engines are designed to day for fuel efficiency and general engine hygiene, and considering the boating industry started out without them, doesn't make sense for them to cool things down....especially when you add ambient temps in Northern climates to the equations.

 

[jimmbo]

Boy that was a quick answer.....it's 3:20 AM CDT here. Flopping around in the bed decided to get up make a pot of coffee and do some gabbing.

Manual says that 2500 is the opening point for the bypass saying that around that rpm is where the water pump develops enough pressure to unseat the valve. Considering how hot engines are designed to day for fuel efficiency and general engine hygiene, and considering the boating industry started out without them, doesn't make sense for them to cool things down....especially when you add ambient temps in Northern climates to the equations.

It's 02:50 MDT here. Jus t haven't went to bed. Retirement is nice not having to get up early

Engines with raw water cooling are kept quite cool, because at temps above 138, the dissolved salts and minerals in the water start to come out of suspension and form Particles. Some of these Particles remain on the surfaces of the cooling passages and over time build up. Eventually if enough build up, the water jackets look like someone ran some cement through the cooling system. The higher the temp the more stuff comes out of suspension. Same thing happens in your vehicles, but they have a limited amount of water that is only replaced when the A/F is. Once all the salts/mineral are out of suspension the process stops. Any time Undistilled water is added, the process happens again. With outboards and a lot of I/Os the water is always fresh. I/Os with closed cooling systems can run Glycol and have a higher temp thermostat. The Heat Exchangers on these units will suffer the problem on the raw water side

 

[Fun Times]

OEM 14856 ...,14586.

Probably a misprint as you have two different parts numbers listed as one is for a thermostat and one has something close to do with DETONATION CONTRL as there are a few other numbers too for this but nothing mentioning a thermostat under the 14856 number.

Mercury-Mercruiser 14856A10 DETONATION CONTRL, https://www.mercruiserparts.com/1485...onation-contrl
Mercury-Mercruiser 14586 THERMOSTAT, https://www.mercruiserparts.com/14586-thermostat-120

Both the end of the link for the Tstat and the package it comes in mentions 120* for part number 14586,

​

833072002, 833072003 833072004 are 143*'s and you can run the numbers in the part number search for what they fit, etc., etc..

And usually the following website is pretty good at putting a list of parts and temps to help chose from, https://bpi.ebasicpower.com/shop/out...stats-and-kits

What engine model, year, serial number are you working with?

 

[Scott Danforth]

,,,,,

Engines with raw water cooling are kept quite cool, because at temps above 138, the dissolved salts and minerals in the water start to come out of suspension and form Particles......

and those particles flying thru the cooling system are an efficient lapping compound

that is why HX's are recommended to be inspected often. even 90/10 cupronickel is no match for the abrasion of the salt crystals.