Rebuilt motor Ina merc transmission and trs drive, put in forward motor pops and dies, go to reverse no issues, shifters have been changed to cables....on water now, any ideas???

Forward puts more of a load on the engine. Could be a carb tuning issue.

Ok, more or less fuel

Not sure if this applies to your set up??
Do u have the F/R cable shifter centering spring on the carbs? If so, it sounds like the kill micro switch/cables are out of adjustment, or the spring is weak & or everything needs lubricating.
When the switch is activated the engine momentarily kills to allow the lower unit gears to shift in & out of gear load free. If there is a load it won t shift. So if the kill micro switch is incorrectly switched it will possibly pop/backfire when giving it throttle when the motor is killing/shutting down.

I'm not sure, I believe the PO removed the factory setup and went to cable and deleted the micro switch, I may be mistaken (any idea on how to tell for sure?) I did find out that if I just slammed the throttle wide open after in gear and moving forward I could sometimes get her to catch and rev up, once she got past her "sticking" point she was great, but every time you went from idle in forward to giving fuel, she'd pop and die.....

Sorry TruxtonFox. Wish I could be more helpful. Maybe someone else will chime in.

Those transmissions don't use a intermittent kill switch. It's a hydraulic transmission and no shifting takes place in the drive. Only switch that is on that trans is a neutral safety switch so you can only crank the engine in neutral. I'm with Griff on the carb tuning issue and the fact that they will bog down the engine more in forward than reverse. May need to back out the idle mixture screws some. What carburetor is on it? What engine?

Sbc bored 30 over, Holley 650 carb

Sounds like a lean pop condition. Richin up low speed idle fuel screws like picklenjim said. See if it even responds to idle fuel adjustments. Might have to jet idle circuit next jet up ?

You asked about sbc performance recipes but never came back and let us know what you did.

http://www.offshoreonly.com/forums/g...n-recipes.html

This will help us give you initial and total timing recomendations and etc....