THERMOSTATS can fail and should be tested or replaced if questionable. The type of thermostat used is important. The only type of thermostat that will function properly is an OEM (Original Equipment Manufacturer) quality replacement!
Older engines that had a 143 degree t-stat originally can use the 160 if you are running in fresh water (not salt or brackish). Engines run at 160 atomize fuel better than 143 and can provide some performance improvements.