Hi, everyone i am new to this forum and have looked through many post but can not find anyone with a similar problem to mine. I have a low hours 3.0l mercruiser that has a pinging noise. The noise sounds similar to pinging caused by detination but timing is set correctly to 2atdc in service mode and advance seems to be advancing to full advance. Fuel is fresh and 93 octane. Carb has been rebuilt twice by a reputable shop with no results. This problem has been goin gon for three weeks and im fresh out of ideas. So far this is what i have done. The motor had a full tune up plugs wire cap rotor, new module for timing advance, new coil, fuel line has a filter and water seperator installed, exhuast has new valve to stop the water from coming back into the motor .... forgot the name of it right now... The noise is not from the outdrive and is coming from something in the engine bay. More info on the boat and motor are as follows, 2004 bayliner 175 mercruiser 3.0l Serial begins in OM the prop is orginal pitch and diameter.... As for the noise it started 7-8 uses ago and was speratic (SP) i heard it at 4k and figured it was due to lack of a tune up.. After the tune it problem still existed carb was rebuilt problem still present next the coil was replaced. Teh next trip i had no problems, then the problem re occured ..... next three trips included check of timing for an effect in the problem with no result, more or less advance does not effect the problem unless the rpm is dropped below 3800 due to sever timing retardation. Now the boat began to backfire after 2k in nuetral no load. The advance module was replaced and currently the boat still has the pinging noise and now backfires at WOT. The noise does not affect performance as the boat will still hit 40mph and max rpm but the noise sounds terrible and can not be ran above 3500rpm. The noise has become almost constant when ever rpm is over 3800 and backfireing occurs if punched to achieve WOT..... Does anyone have an idea what could be my problem??? If any more info is needed or an clarification is needed please let me know and thanks in advance for anyone who can help.
