2nd ignition coil after failure after a 1/2 hr ? what would cause ?

[al1026]

Twin 4;3 GXI
2002
ignition module failure , 2nd time , within weeks
Had a raw water pump failure spraying salt causing damage too many parts
Salt sprayed was pushed up hitting alternator , alternator thru salt all over ECM , Throttle air
sensor , , Coil pak , Alternator ,
Starter also seized , Possibly a coincidence ?
Hired a mobile VP authorized service tech too change starter , Hated too do so , changing a starter is simple except I cant get down , He had too remove manifold / riser
Hours later completed , cranking , no start , Prior too starter seizing boat was starting
His first thoughts since ECM was hit with salt , possibly no start cause since no spark ,
Had inventory of a coil pak , Installed , engine fired up , . He said GOOD ECM very costly
He did say change that alternator , not putting out proper volts , will do damage too new coil
Original VP alternator costly , went after market 65 or 70 volt. Installed fired up , GOOD
Would start at dock , let idle 10 minutes , seemed ok , Took out few weeks ago and after 40 minutes engine died
Back too dock , coil not getting spark
Calling tech , parts under warranty , he came down swapped , Never checking what caused Coil Pak too stop . He did pass a remark , DID you use boat with bad alternator ? NO
Yesterday Same , 45 minutes , motor stopped , Limped back one engine ,
These OEM parts are costly , I have a NAPA coil part , same as the vortec engine , installing as a test , This guy is not going too warranty a 3rd coil , He never test anything just threw parts
What else would cause a coil pak too fail ?

 

[al1026]

FOLLOW UP
Down too boat yesterday ,
Purchased module as back up , Box store , chevy vortec .
When engine stopped I was close too land , no danger , jumped into engine room , First thought, Problematic external fuel pump cells.
,Always hitting them and possibly one of the wires came off.? ( good )
Checking coil too see if spark plug wire did not come off , felt some water on coil ?
Decided too return too dock on port engine ,r
Posting other day ( no responses ) my initial thought , ( damn )
coil pak failed again ? since other coil failed ? so fast , ? so I thought ?
Repair guy flipped coil from other engine and it did start , so it was NG
I would not hire a guy too do work I can , changing a coil but he was there too change starter . Having too remove manifold / riser move hot water tank , Arthritis stops me , but engine would not start and turned out coil was also NG ,
Yesterday , testing , fuses , relays , ignition relay not making contact , Fired up once I wiggled , But the water I felt was coming from the exhaust boot , off riser hitting coil , Maybe it stopped cause it got wet ?? DONT KNOW , all I know I got it corrected , Need too return with boot ,
I have a number of mercruiser boots from previous boat , not sure if it will fit ,