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1997 mercury 150 2 stroke carburated

Spencer0731

New member
I have a 97 mercury v150. Engine only has 300 hours and is strong and runs perfectly except for one issue. As long as I'm running on plane its perfect. But, when I cut it back to trolling speed, 1500 rpms or so, it will go along fine then all of a sudden it sputters for just a second then the alarm starts blasting. Once I turn it off then back on I can put it in gear and take off and run all day until I try to go slow. I changed the idle speed control module, the oil pump control module, it was charging too much and the tach didn't work so I changed both voltage regulators (that fixed the charging and tach problem). I replaced both temperature sensors, thermostats and the oil reservoir level sensor (the wires were twisted and one was bare) But, still nothing changed on the low speed alarm that goes off. Changed inline fuel filter on engine and put in new fuel lines and new water separator. Anyone have any idea what else could set off the alarm on that old of an engine? Thought I may order a new trigger. I know the stator is working fine because it charges great. I really want to fix this engine. Boat and engine are like new except this issue. Thank you. Oh, and my engine is the type that has 6 separate coils and NOT a power pack
 
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Already installed new impeller, thermostats, both heat sensors on the heads and the water flows heavy. Plus, it hesitates first like if you hit a small stick, then alarm goes off. Restart it and it runs fine. I can idle it in neutral all day, only goes off while trolling slow speeds.
 
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