We have a 350 TBI motor in our boat and it has had a problem with fouling the spark plugs to where they will barely fire at all. We have replaced every sensor and the fuel injectors. Timing is dead on and fuel pressure adjustments have no effect on it. It seems to bog and then pick up fine when you slowly increase the throttle to WoT but when you give it wot from idle it with DUMP fuel in and then backfire out the intake. I am new to TBI motors and can't figure this out. Any help would be greatly appreciated.

Also the entire ignition system has been replaced.


Thanks,
Nick

 

Might not be advancing the timing.
When you checked your timing did you unplug the spark control module?
What kind of distributor? Vaccum advance or electronic?
Is your Spark control module good or new?

 

It has an electronic advance. The spark control module has not been replaced. How do you test it?
When I set the timing i unplugged the module, yes.

 

UPDATE: The module was bad so i replaced it but it did not fix it. It is still backfiring out the intake. Any ideas?

 

Plug wires on the right cylinders? I've done that before. Something is wrong with the timing.

 

you might think about changing the plugs
to 'hotter' plugs

 

Wires are fine we have checked them over and over. Plugs are NGK TR5 gapped at .040.