Why is there 2 different Thermostats available for my Engine

[redlowrey]

On the same day?

No mate Winter summer

[D'oh999]

Well here is the closest Old Thread I found about 2 Thermostat Temps? And what does it mean? and which one to use?

I have the original 140 Thermostat. I run Fresh Water from 34F-75F-35F water Temps (Spring-Fall any sooner or later the motor doesn't trim down).

I understand 4 strokes need some heat and the Cooling System is abundant, so wouldn't the 170F make more sense? I could see a 140F on Heavily Worked, Nonplaning Hulls, butt normal cruising motors should benefit from being slightly warmer.

[tsturm]

I have a 2013 DF90A and there is a 140f and a 160f thermostat available, now i read most raw water cooling systems typically have a lower temp thermostat than a closed (anitfreeze) system, but why would there be 2 different ones for the same engine ? My engine came with the 140°.

I trailer the boat, use in salt water and flush every day.
Just wondering if maybe the 160° may be the better choice since it will be more efficient, a little warmer, and maybe prolong engine life ?.

There seems to be different opinions on this, but does anyone know for sure why i have a choice ?

Thanks

I live in Alaska's Cook Inlet area, sea temp varies from 27* F to maybe 55* F. I put in the higher temp stat., to get the engine to run at 164* F