Engine Alarm Won't Shut Off
First a quick thank you to everyone on here. I've lurked TT for almost 10 years now and I can't begin to tell you how many questions i've found answers for in these threads.
So thanks to everyone!
I'm posting today because I'm absolutely stumped.
I replaced the original alternator on my '88 Tristar 351W with an alternator that my father-in-law recommended (he's a retired cert Mercedes mechanic so I didnt really question his advice). At the same time, I replaced the impeller(I normally replace it yearly). After installation, we headed to the lake to test. Boat fired on the first turn(as usual). Volts were higher than expected(14-15 volts) at idle. I let the boat run for a bit on the trailer to warm up. It warmed up and then began to overheat. Immediately shut it down when it hit 200(*no engine alarm) and checked the impeller. It was partially chewed. I was in a hurry when i put it back in and knew in the back of my mind that I had rushed it. Good news, I always have a spare on hand. Replaced the impeller CORRECTLY this time, and began again. I let it warm up to 165 and the temp held this time as per normal. Moving on to test the alternator, I began to rev the rpms. First rev to 2500 rpms pinned the voltmeter needle to 17 and sounded the engine alarm. It was only revd for about 4 seconds. I let the rpms return to idle and the voltmeter returned to 14-15 volts. The engine alarm continued to sound. I shut it down and when I turned off the motor, the main circuit breaker tripped(weird?). I pressed the white circuit breaker button back in. Now the engine alarm sounds when the key is turned to the on position before you even start the motor and the tach quit working as well.
As it turns out, my father-in-law had assumed that there was an external voltage regulator and so the alternator he recommended had NO internal regulator. We have since replaced the alternator with the correct internally regulated alternator and everything on that front appears to be good. However, the engine alarm still sounds when the key is in the on position, even when the boat is running(tho the tach still does not work). The motor fires on the first turn and the voltmeter reads 13 volts at idle and under load(theres a little fluctuation depending on battery charge). Temp guage is working and oil pressure guage reads fine as well. Everything seems to be running the same or better than before the alternator replacement, except for this friggin alarm and the tach.
I've spent about 20 hours over the last week checking grounds, wiring, fuses, relays, etc. and I cant figure out whats making the little alarm sound off. No visible damage(melted wires, terminals, etc.) anywhere to be found in the dash, doghouse, or battery compartment. I can unplug the engine alarm board in the dash and the beeping obviously stops but I would prefer to solve the problem instead of unplug it. My understanding is that the alarms sounds for high temp, high/low voltage, high/low oil pressure. Could it be falsely stuck on? Is there a way to 'reset' this alarm on the older boats? Should i try to replace the engine alarm board? Where would I find it?
My local dealer had no clue where to point me. The dealer's solution was to bring it to them but I am hesitant to bring in an electrical gremlin that could rack up $hundreds in labor alone and take them a month to fix(over the Forth no less).
I'm going crazy here...
What have i missed?
Thanks ahead of time for any consideration!!