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1986 mercruiser starts hard


skip15's Avatar
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Join Date: May 2008
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05-21-08, 07:17 PM   #1  
1986 mercruiser starts hard

I have an 1986 mercruiser 120 hp it take about ten cranks to start an then run rough for awhile but after warming up it runs great i think it's the choke can you st thyis choke it's an electric choke it;s doesnt high idle at all

skip15

 
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thezster's Avatar
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Join Date: Aug 2005
Posts: 2,268

05-22-08, 09:19 AM   #2  
You're probably correct in assuming it's an electric choke system. Time to check it out. Take off the air cleaner/spark arrestor and see where your choke plate is sitting. Should be almost closed without any power to the system.

Turn the ignition to the "run" position and watch the choke plate. After a few minutes, it should begin to open up slightly until it reaches vertical (full open). The system is designed to make the engine run rich for a few minutes - then the choke opens up to lean out the fuel mixture as the engine warms up. If this above doesn't happen, or the fuel plate is too far open at the start, then the engine isn't choking properly. As long as the choke coil is working properly, it's an easy adjustment to richen up the mixture at the beginning of the start cycle. Loosen the 3 bolts on the choke - turn the housing until the choke plate is almost closed (open about 1/4inch or so) - then try it. You may need some trial and error, adjusting each time the engine cools down enough for the choke plate to close back down.

 
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