1988 Merc XR4 150 Black Max uneven idle

steve_h7

Chief Petty Officer
Joined
Sep 16, 2018
Messages
401
First boat I've owned... rebuilt hull and now trying to figure out outboard.
Serial number OB381704. After sitting through the long rebuild it would start but wouldn't idle. Replaced plugs, fuel filter, rebuilt carbs with new needle/seats. All hoses between tank and motor are new. I did add Seafoam in desperation to get it to idle which actually did seem to help a little. Reading past threads here I learned how to adjust idle without a idle mix screw so now idles pretty well but races and falls randomly. I'm not sure if I'm looking for an air leak or ? Appreciate any guidance! I'll try and include a video of the tach. It's hard to hear the engine but it clearly is idling faster and slower.
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