First two indications I pick on when this happens is contaminated fuel or restricted/clogged jets in the carb bowl. 
It don't matter either way, I'll usually pull the bowls and clean the carbs. Normally fixes the problem. If not then at least this part is off my mind.
		 
		
		
		
		
		
		
			
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'75 Cuddy with '00 Johnson Ocean Pro 150 horse
 
Benny
  
  
			 
		
		
		
		
		
	
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