smoke, if i understand him right, tube is coming off the block under cowling,  
i thought the speedo comes off the lower unit. 
 
if he's got a schematic, should be able to follow to source or if it pees on a hose, part of cooling system, if not, speedo. 
 
either way, not that hard to trace
		 
		
		
		
		
		
		
		
		
	
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