crusader marine 454

Blocked jets from sitting too long and the fuel in the carb turning to sludge would be a good thought

Q-jets or Holly carbs?
Highly un-likley that there is fuel in the bowl and the accelerator pump(s) (squirters) are not squirting fuel.
So, How do you know your getting gas?
Stuck carb floats, stuck fuel pump check valves, leaking filter low side of pump and bad hoses I have witnessed.

TBI has to be turned on. more than likely a electrical problem. Look for a crusader relay or breaker usually mounted on the stb riser, opposite riser from the ECM.
Do you have a manual or schematic?

Please be careful; Gas and electricity can get exciting, even deadly.

There is a relay under that cover. If the other engine is running, swap the relays.

This rely turns the ECM options on. This energizes the TBI.
You may or may not be getting a reliable spark also.

It's one of those relays that help the engine get a full 12Vdc charge to the options and not have all the current go thru the key switch and all the way back.

I had to dissect one of these Crusader 454s once and purchased an ECM module. Was lucky when I found that relay was old and not passing the required current. Since then, I have hit the nail on the head on some similar failures.
It may show 12 Vdc on the output when testing a non running motor, but there is not any current flowing thru the micro contact. When the starter engauges, it's flat lined.

It will take you a few minutes, but worth the experiment.
As soon as you get that cover open, make sure the oil fill cap is back on. lil screws, short (real short) wires, tight place for lil fingers.

The Crusader relay is about $60 and usually has to be ordered.
I've started installing regular 40 Amp square relays and mounting them out side the cover (with new pig tail socket) and leaving the owners with spares.

Or, call in a tech. Remember what I said above; Gas and electricity can get exciting, even deadly.