you have a plate on the cylinder head, called a water jacket. you have to remove that plate and the tstats are in the lower end. while there replace everything. tstat gaskets, popet valve spring and gasket. you can see diagram here, under crankcase. http://shop2.evinrude.com/ext/index.aspx?s1=bf6ad09c53cead335fcfd8a6471c0f7f
