I have a 1999 42 Lightning with 500 efi's My port engine pops in the plenum at 2200 to 2400 getting on plane. I can blast pass the pop with no problem. The boat idles fine and runs great at speed. Does this sound like an ethanol problem? Thanks in advance Daryl

top ends redone year prior , valves ,springs ,lifters ,rockers
fuel pres. 41 psi.
new cap rotor plugs
new 36lb. injectors
no codes active or stored
all readings on scanner normal
swop tp sensor , map sensor , dist. module , ecm`s ,cts , ait ,
valve adj. redone and springs ck. OK
lean condition between 2200-2800 rpm thottles uneven til 2800 then picks up.
if held between 2200-2800 will cause plenum pops but not consistant
between 2200-2800 if fuel is added to plenum the motor will pick-up 400 rpm
the boat from 3000-5250 runs perfect and thottles even. never pop

Here are some things we have tried any other ideas?

I guess that you have changed the fuel /water seperaters?

my 502's do the same thing if i really load it up trying to come on plane too hard and drag them down... my feeling is that the engine management system gets into an area where it is a little lean... big throttle position, low revs, no vacuum, timing who knows where... i think it just ends up in a lean part of the curve. if im just a little bit careful how i lean on it it never does it.

every weekend there for a while

ttt nobody? This is killing me! Thanks in advance Daryl

if you are desperate to try something, and it really bothers you, then i would try two things.

first, i would have all the injectors out and , with the scanner set on pulse and a seperate stand alone fuel pump and fuel supply rig, test each one for the quality of the spray pattern. if its a nice smooth fan... thats good. if its big drops and dribbles or weak, then that will make it lean at short pulse width without making it run bad at speed or idle.

i would also get some injector cleaner of death and run it thru at the same time as well as back fush them to clean the screens. when they all pulse and fan nicely then you are done.

and then if it still does it, i would put a couple more degrees of timing in it. the knock sensor will take care of you if you go too far but if it isn't advancing quickly enough or is retarded a bit, it will cause this problem.

New injectors will try the timing again Thanks

Your fuel pressure sounds a bit low, I would try turning it up to about 43-44 lbs and try that. Its worth a try as a simple test.

Best Regards,
Ray @ Raylar

thanks! bumping it up