ok guys, this one is kicking my ass and has me going nuts.
rebuild engine installed, 5.7, thunderbolt 5 with knock sensor. 4 barrel weber. proffesionally rebuilt carb, new knock sensor, new mechanical fuel pump, new ignition sensor and coil, new plugs, wires, installed remote fuel tank to insure good clean gas. timing checked several times , base and advance system ok. the boat will idle and rev in neutral all day long but put a load on it and as you pick up speed and rpms, you'll hear it pinging, if i do not pull back on the throttle, it will backfire and stall out but start right back up. and act the same way.
the timing is set up 10 btdc. firing order is correct..The carb was rebuilt and then after the 1st occurrence I brought it back to him to go through it again with this issue in mind. He found nothing wrong.
yes, ignition parts are merc. cap/rotor , wires, coil, plugs. all new
even when it is detonating, it still runs smooth, no vibration, no stumbling, nothing to indicate an issue.
last trip out, i tried moving the distributor, and still had detonation advancing and retarding timing
http://www.marineengine.com/boat-forum/newreply.php?do=newreply&p=718927