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Old 03-23-2013, 07:46 AM
Mark rsa2au's Avatar
Mark rsa2au Mark rsa2au is offline
TT Enthusiast
Join Date: Mar 2013
Boat: Mastercraft X5 2001. 310hp preditor
Location: Australia
Posts: 182
Now I am stumped!!!

Motor still running very rich, black smoke from exhausts and black sooty plugs from an hour on the water. Also backfiring over 4000rpm!! Dream boat not so much fun anymore

This is what we have done so far:
IAC broken unit replaced with new one - working perfectly.
Injectors reconditioned, all good. Also tested with New injectors - no change. New injectors had same flow rate as old injectors ( I wonder if old injectors were swaped for bigger flow units at some time)
Fuel pressure tested with dodgy fitting onto guage. Read 25psi before leaking so I think 30psi would be a safe bet.
ECT tested as above post, all good. Reading a little high but at least telling ECM it is HOT.
TPS tested as above post, all good. Replacement part no change.
Map sensor tested as above, all good. Replacement part makes no difference.
Plugs changed & gaped at 1.3 (from factory) will adjust down to 1.1 tomorrow but should not change issue above.
Distributer cleaned.
Timing checked as per manual and 10degree BTDC @1000rpm. ( floats a little on the timing light - not rock steady but easily visible).

What the hell else is these to check - service - replace to stop it running so rich and stop the backfiring?
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