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'96 PCM 351 "Coughs"

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kevinjgould

New member
my 96 Boomerang has the PCM 351 and ran really well for the first 5 years I had it. Now its developed a "cough" at higher throttle levels. I've had the carb rebuilt and changed the fuel filter, but no improvement. I checked the spark and timing, and both are fine. Any ideas?
 
Ayuh,..... A cough, or backfire is usually caused by a lean condition,.....

Water in the fuel,.... crud in the carb,.... old rotten gas are but a few possibilities,....
 
It could be that your progressive timing advance isn't operating properly. When you checked the timing, did you check it at mid- and higher RPM, or just at idle?
 
Sorry, but I don't know the what the curve is for your engine. I'm just a boat owner and I had that backfire/cough when throttling up. It turned out to be lack of timing advance. I will say that if you watch the timing mark with your timing light and smoothly increase the RPMs to say 2000, you should see the pulley's timing mark move away from the timing tab.

Hopefully one of the pro marine mechanics on here will chime in.
 
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