Removal of thermostats

[steplift20]

My engine is a 150 Mercury outboard has two thermostats the call for 143 degrees. , what would happen if I removed them? The reason is because my engine over heated and I want to see if it is because of the thermostats or water impeller , the mechanic up here said that will be fine to take them out. Because I'm a cheap bastard I bought after market thermostats to save $15.00 learned my lesson. By OEM