Would start for less then a sec then die

Totally different motor but I had a Corroded Fuse that caused that. Find the fuse that controls that and wiggle it with the key on next time it does it.

Chris

Ray this.is an original version vst.[ATTACH=CONFIG]552193[/ATTACH]

Well, I figured out why I had no beep (would crank but not fire off).

Ended up being a loose spade connector on the S kill switch. I pulled dash off and traced wire from kill switch and still didn't beep. So I took key panel off again and started playing with connections behind kill switch. AND there it was. I recrimped the connectors and she's good!

I typed too soon on mine. It started working better, but still not a strong buzzer. So I cut and stripped and replaced all the connections behind both switches and kill switches.
NOW, I figured it out!! The D$mn switch!!!! Worked some times and works perfect others. Only found it bc I was playing with the key when it didn't buz and then it buzzed while playing with key.

POST # 26 the engine serial provided by OP has the VST fuel system. the engine is listed as 1996.

At first he reported a 1998 engine as in 1998 there was no VST fuel system for those year models. Hope this helps whomever. IMO might be best someone refer you to a Mercruiser trained mechanic and or shop with a trusted name. No offense to you. Good luck

Just for confirmation purposes! Yes you are correct with your engine model, if you cycle the key to quickly the audio warning horn circuit will not have a chance to reset itself within the MEFI ECM thus not sounding the horn with each key up without allowing roughly 10 seconds of rest in-between key-ups. My personal 1996 454 mag MPI is the same way plus I have noticed it multiple times in the past on many different boats of that era.

If it is vapor lock, then try doing a search either here on OSO in the upper right hand corner of each sub-forum page (or google online) for vapor lock Mercuiser 454/502 Mag MPI as there's lot's of info for this issue. One trick of many is sending the fuel return line back to the fuel tank vs back to the water separating fuel filter adapter housing from OEM stock.

Hope this helps, good luck.

THIS ANSWER just saved a marriage today. Thank you!!