Still having problems
I installed a new tps and map sensor no change. Also checked output from TPS and it is stable and the correct voltage like .6 to 4.5 volts. I tring to get a moble mechanic with the mercruiser G3 program out to see what he can see with the computor connected. Any additional ideas are welcome. Does anyone have the pin layout for the ecm so I can check voltage at the ecm plug?

Thanks
Joe

If new issue after putting in new engine, could be bent or loose pin in ecu or any other harness connection.

So……with all this engine running did the compression go from 90psi back to healthy normal 170psi or so ?

Have not rechecked the compression. Do you think it would hard start with that low of compression? Also with tps dissconnected throttle up seem vary solid and quick response.

joefran
you said you replaced the plugs, for the hell of it put in a new set.......
i never had a "set of plugs" issue beyond an occasional bad plug with any of my boats but back in the 70's with my Z-28 i got a bad batch(s) of plugs....
i worked as an aircraft A/P mechanic at the time and when I tested the plugs on an an aircraft plug tester that applied compression and spark to the plug, only 2 or 3 fired over 50psi applied........ I got a new set from the same parts store and had the same issue, turned out to be a bad run of Champion plugs at the time.
if not the plugs, see if you can borrow a carbed intake manifold and run he engine old school
good luck

Joe,

I don't know what your exact problem is, but it originates from this right here. Do you have a way of checking AFR? Source a set of WBO2 plates and sensors and find out what's happening with and without your TPS connected.

Thanks. Brad.

if I am reading this right the original engine was a 305 and now it is a 350 but is using all the parts from the 305 except block and heads. this also appears to be a flat cap distributor motor. if so is the dist in correctly. you set it to TDC of #1 and then install the dist with the rotor pointed to the mark on the body and lock it down as the ecm handles everything else. trying to make sure what parts are used as there was a time where some components switched the wiring. I know on certain MAP sensors they swapped the + and - wire location at a certain point depending on what MAP sensor you have but not sure if that happened with the TPS as well.

you talking about this distributor set up,