1993 four winns 5.8l will not stay running.

I have a 1993 four winns with the 5.8l omc last year it would run but this year I can not get it to stay running. The motor will crank and try to start until I let off the key then it just shuts down. If I hold the key on it will basically come up to an idle but then when key is released shuts down. I have already replaced fuel filter and removed the anti siphon valve because it was snapped off when tank cover was removed earlier this year. It almost seems like something is shutting the fuel down when the key is released could the ignition switch be bad or are there any fuses in the system. I motor has spark checked at the plugs when cranking and the motor is getting fuel when cranking. Any ideas would be great thanks.

could the ignition switch be bad

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Ayuh,.... Sure could,.... The ignition fires off the Start circuit(yellow/ red wires), til ya let off the key, which switches the ignition to the ignition circuit, the purple wires,...

So check the keyswitch with a test light, the ignition post, usually purple wire, should be Hot, with the key in the "On" position,....
If it is,....
Move to the motor, 'n check where yer loosin' it,....

Definitely was in the switch so now I can at least get it running. now to fix all the other problems will start on them another day after I get new switch installed thanks for help on that one. I will post again if I have issues fixing the other things wrong with this boat being as it has been sitting for awhile.