1994 larson with 3.0 mercruiser replacer throttle getting nothing when trying to start engine good batteries hookups good everything else works looking for suggestions

Mechanical fuel pump most likely has a bunch of aluminum oxide formation plus the filter inside of it is completely gone and callaseped causing restrictions. The carb will need to be overhauled and I bet the filter inside of the carb fuel inlet is completely full of crap restricted as well. This will cause no or barely any fuel flow internally to the carb. Very common problem with these and the filters in the fuel pump and the inlet of the carb again very common.

Next the distributor cap and rotor possible internal corrosion so check for spark on all 4 's with inline spark checkers. Buy the completely seal ones that hook inline with to your spark plug wires to the distributor cap terminals.

you need fuel, spark, air and good compression - IMO fuel is the problem here and possible spark might need to be address as well