I have a '88 30SS with the 330 454's. I swopped the 55 amp alternators out for 140 amp alts today. I started the port side and it fired right up. Turned port off and started starboard side and fired right up. With the starboard side running I tried restarting the port side and turned over, but no start. The starboard side died seconds later. Now I have no "fire" to either engine and my dash/gauges area dead.
Thinking the new alts are too much or something and blew a fuse or relay somewhere??? PLEASE anyone have a clue where to look? All the glass fuses underneath the dash panel appear to be fine and everything else works and has power.

i would check all my conections and grounds first sense you say you just swopped the alternators and go from there.

what about the breaker on the engine, the red button mounted near the carb. Did that pop?

#1 Check the red breakers
#2 Disconnect the alternators and see if they run

Checked the red breakers right away. When those pop the motors will not turn over. Guess I'll try disconnecting them to see if that changes anything. Something has to be blown or tripped tho I feel because no ignition to gauges? Thanks for the thoughts!!

Some of the boats have circuit breakers that look like light switches under the rear seat that will disconnect power from the boat. Just a thought.

Ok so I learned that what happened is that my safety lanyard switches got blown out!! So, now to figure out why it's happening. This make sense to anyone that installing higher amp alternators would do this and why? My tachs are going crazy now too.

Better check the voltage output of those alternators. Their output (amps) should vary with the electrical load, and to some degree rpm (max output is usually 2200 to 2500 rpm's). Voltage should not exceed 14.9v.

Are they marine alternators? Are they single wire alternators?