Hi guys,

I have a big issue with my mercruiser 575 sci, it’s fauling my spark plugs in 3 min running than the enginge won’t start
after put new sparkplugs it will running fine again but wil fault them again.,
I changed the NGK number 8 to number 7.
i put new distributor cap and rotor also new coil.
when reving the engine black smoke is coming out of the exhaust it looks it’s running verry rich.
what else can i do to put my engine run fine again.

Are they getting up to normal operating temp ( around 145*)?

See if injector is leaking and if engine temp sensor is correct

575 sci had a lot of injector problems - if plugs are fouling it is more than likely a stuck injector. They are an oddball injector that is NLA, and there is no satisfactory aftermarket replacement available. Check with BUP for having them cleaned and tested.

You've probably already found in a search here, but Eddie Young has a nice throttle body / injector setup available. It's a custom rig that he designed - but if you're having injector problems, there are really no other options (for a close to stock setup).

you can pull your injectors and send them out to be tested. If you need help with that end let me know. I can help.

Also what is your MAP readings while running at idle and thru out thr rpm range ?

how is the ignition side of your engine ?

OP started thread on FEB 6 and has not been back on OSO since FEB 7.

I have Injectors with less than 100 hours on them if you are interested let me know

have the injectors checked and cleaned also you need to check fuel psi we had one that the fuel psi too high would foul the plugs changed the regulator fixed the problem,we can clean and check the injectors if you need some help