Biggest issue i had was the rubber grommet getting crusty. I usually changed em every 2-3 years, but checked the annually.  I would change the poppet valve assy at the same time. 
 
Also, when buying t stats, water pump kits, poppet valve kits  on merc s, i would recommend OEM stuff.
		 
		
		
		
		
		
		
		
		
	
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