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87 Mariner 50 hp 3-cyl Idle adjustment

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pbarbeau

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Need help adjusting the idle on my 50. Doesnt idle bad when not in gear but does not idle very good when in gear with it backed all the way off.
 
Check compression. May not be running on all cylinders. Start idle screws at 1.5 turns out from fully inward.
 
The trick to get that motor to idle is to use an infrared heat gun. Aim the red dot at the plug's metal base and twiddle the idle mixture screws until you get the three plugs the same temperature (about 90 degrees). It takes time and patience, but that's how I get them to work. Finally, ad 1/4 turn OUT (CCW) to each idle mixture screw.

Jeff
 
The motor is running on all 3 cylinders, compression was good motor ran good except idle. Which is the Idle mixture screw is it the one on the left on the carb when looking into them?
 
fastjeff said:
The trick to get that motor to idle is to use an infrared heat gun. Aim the red dot at the plug's metal base and twiddle the idle mixture screws until you get the three plugs the same temperature (about 90 degrees). It takes time and patience, but that's how I get them to work. Finally, ad 1/4 turn OUT (CCW) to each idle mixture screw.

Jeff
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Does this apply to my 1988 90hp triple also?
 
No. That motor has one carb per hole, as it should. The earlier triple has 2 carbs per three holes, which makes adjustment tricky.

Jeff
 
Jeff, took it out today and adjusted idle and was great till I went to go WOT. Just Bogged down. Never would pick up. The past week ran fine just wouldnt idle. When going WOT saw that the top carb was only one opening. Pulled boat out went home found there was no key in the coupling assembly in between the carbs. Put a peice of metal in there and went back out and ran the best ever! Thanks for all the help I found on this site!!!
 
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