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-   -   Is it me or the Dealer ?? (https://www.offshoreonly.com/forums/general-q/288300-me-dealer.html)

AllDodge 12-02-2012 09:04 AM
Originally Posted by Young Performance (Post 3824003)
You stated that they were crate engines. Did they come from Merc? If not, they probably do not have the same cam as a Merc. 502 MPI. That alone will throw the tune out in left field.

If it's idling at the correct rpm and just rich, then there is nothing wrong with the IAC. If the IAC was acting up, it would not idle correctly.

Verify that the fuel pressure is correct. Check to be sure the ignition components are in good shape. If that is all good, then my suggestion would be to get an O2 sensor in it and see what the AFR's are. If it's rich, it will show it. You will need to install O2 bungs in the exhaust pipes in order to use a wideband O2 sensor. Also, see if there is any way that you can verify what camshaft is in the engine.
Eddie
The engine came from an outfit in massachusetts, I think it was marine engines Inc or something like that. The company has since changed names a couple of times. The motor is about 5-years old. The engine idles fine and preforms fine until it fouls the plugs (every 2-years). I thought a 502 was a 502 but I'm no expert so as you say this could be my problem. I know what an O2 sensor is but not AFR's. Keep thinking about pulling the motor and getting a factory complete setup and hopefully get rid of all these issues. I like the sound of the 525 but this forum has mentioned it doesn't have to low end torque I probably need to get my 10K lb boat out of the water. Also my standard Bravo-3 is at it's limit with 415hp.

keith2500hd 12-02-2012 06:31 PM
AFR=air fuel ratio. water temp low is biggest cause for fouling, ecm goes runs in choke enrichment. you at least need to know what is in engine, need to get or make inspection list. mercury's fuel injection is taylored for specific build-up(speed-density cal's). an option, could switch intake and go to holley efi(only uscg approved), use O2 sensors to have it self calibrate. search, was big discussion before. think they just need to start machining O2 bung's into risers, there are spacers that go inbetween risers. if interested check KE or cpperformance sites.

speeddr2000 12-02-2012 07:23 PM
if you have a 502 with a different cam even heads that the merc 502 mpi was set for your gonna have problems its ment to run with in the specs that merc gave the ecu. i would have a tuner flash the computer.


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