Does my outboard have a thermostat.

[kevinspage]

Mercury Mariner 40 4cyl 2 cycle serial # 0D060736.
None of the thermostat parts lists show my outboard or any other 40hp Mercury outboard.
Do any 40hp Mercury outboards have a thermostat?
Thanks!
~Kevin.

 

[Chris1956]

Looks to be a 1991. One would expect it to have a thermostat, however, I could not find one in the parts diagram.

 

[ThomW]

Yeah. That is interesting. I see the temperature sensor...but no thermostat....

 

[Texasmark]

I don't think any of the originally designed, 4 cylinder Mark 30 or Mark55, or the 6 cylinder either up to the Mark 1000 first 100 hp outboard type power heads ever had a thermostat.

 

[kevinspage]

Looks to be a 1991. One would expect it to have a thermostat, however, I could not find one in the parts diagram.

Nope not there. And if you look at the thermostat parts pages none of this type 40 has one. Weird. Temp is important to engine performance but not having a thermostat makes for a simpler design with one less point of failure.

 

[racerone]

Agreed-----Many Mercury outboards never had a thermostat------The 4 cylinder 2 stroke from 1954 to the mid 1990's never had a thermostat as far as I know.

 

[racerone]

Later 2 cylinder 35 and 40 hp did have a thermostat added.-----The 7.5 / 9.8 had a thermostat for a few production years.

 

[jimmbo]

I think the 2 cylinder 400/402 was the first Mercury to have a Thermostat. In 73 the 3 cylinder 65hp got one too