Hello i need some help.

I have 502EFI 1993 vapor tank style
ECM reprogrammed to 9334 HEX
Base Time are 8*
Daicom shows me at accelerate max of 40* than at WOT 29,53* The Advance timing light Diagnostic tool show me 29* on it, than i have the light at 0* on the Crankshaft Mark 0*.
Diacom show me the real timing.

3062RPM 34,45
3135RPM 34,45
3561RPM 28,48DEG Spark
3723RPM 33,05
3773RPM 35,16
4915RPM 29,53 ?????????????????


Why are the total at WOT dont go to 36* (33-36*) ?????????????

Are you getting your numbers in neutral or while actually running the boat under load????

Hello Griff, this are under load.
I have twin engines and both are the same.

Have anybody a diacom data file record from a 502 efi under load in WOT for me ?
My email are [email protected]


My first 2 Ecm's are hex9550. The secound 2 emc's i have are reprogramed with the data from the 9550.
If the 9550 have a wrong program over 3500rpm the wrong file are copied to the new ecm's 9334.
Ore is it normal over 3500 rpm to go down with the spark advance tho 29,53 ?