Worked on a friend's '85 SN 454 last night, due to intermittent starting issue...

Sharing results for posterity here..

Never an issue cranking, but not firing 10-15 minutes after a hot shutdown due to no spark.  

Witnessed it once catch upon returning key to run from start, so sourced a new keyswitch, but also suspected the pertronix is not seeing best voltage to function while cranking.  Battery is large as can fit, and not deep cycle

Pertronix ( first gen) is seeing full voltage available and the coil hot sees the resistor, as directed

about four connections needed snugging up, at starter relay, the main breaker, and the at the 10ga wire terminal on the buss at the dash

Additionally, and reason for posting, is the following....

the boat has 10ga from engine to dash bus - that is good

HOWEVER, from the  ignition breaker switch on dash, there is only a 6" 16 Ga jumper wire to the keyswitch input hot.

Also, the run terminal was also only a 16gauge wire that daisychained to two other gauges, before it finally exited into the bundle and QD's, out to the engine

So, the whole ignition and dash runs off a single 16 gauge wire, to three other 16 gauge wires, daisy chained using  3-4 crimp terminals before going out to do broom broom stuff

  this appeared to me to be factory wiring, unmolested

The keyswitch was replaced

The weak jumper from IGNITION breakerswitch to IG HOT was replaced with a doubled-up 12 gauge wires in parallel

the purple wire out to the bundle, was snipped from its last daisy chained gauge's terminal, and now goes straight to RUN on keyswitch

My friend reports it now starts better than it ever has,  since he's owned it from new 

Perhaps this will help you,  and we'll likely keep hearing about starting issues from these vintage boats, as this was untouched factory wiring

Note that this engine is manual choke, so the voltage drop would be even worse with a more typical electric choke config

JQ

Didn't find anything wired backerds

No gain since you already added some wires in the dash but a relay in the purple wire ignition circuit would eliminate the need for the new dash wires.  Same results without relying on the dash wiring for your ignition operating voltage except enough to keep the relay energized.

Was there a reason you didn't run everything through the relay on your boat?

Also sounds to me like CC must have wired that boat on a Wednesday, that's the day they just used whatever leftover wiring was hanging around  

If that really was a 16 gauge wire and original, it was a mistake.

The purple ignition wire mentioned in the first post is a 12 gauge wire from the keyswitch back to the engine for comparison purposes

Somebody else with a same era SN needs to climb under the dash and see what that wire to the keyswitch  from the breaker is

i found that during crank, with ignition on a relay,, the continuous duty accessory relay i was using, (and still using 20 years later) a hella, was just on the edge of actuating  during crank, causing occasional crank no fire till release key. since then the starter has been replaced with a perm magnet starter, it would probably be ok now. I don't care to.  But i can switch back and forth between direct and relayed ignition by moving one connector on terminal block on the back of the engine.

but i know if i had a marginal battery for any reason, i'd be stuck no start bacuse the ignition relay woudn't close during crank. Hence i go direct on the ignition.

I didn't rewire his dash, just replaced a 6" jumper, and moved to purple wire direct to the keyswitch as it should have been 

"the blue wire with the white stripe, NOT the white wire with the blue stripe."

Quiz: Is that the tip or ring?