I need some electrical experts here.
This boat is new to me...
I bought it knowing it needed lots of things done. The engine is a 1998 Mercruiser 350 Mag Mpi with a Bravo 3 drive. I bought it knowing the batteries were shot. I hooked a new battery up, launched it and it ran great. I parked it in a slip and took a few weeks to fix some things, and found the alternator was bad. I replaced the alternator, which I is all I did to the engine.
I then took her out and found she was really down on power, and then stalled a few times, restarting each time. I got a suggestion that if the alternator was the only change, maybe that's thnproblem. I disconnected the alternator and she ran great but was still low on power. No stalling whatsoever. Hooked thenalternator back up and the stalling was even worse. Threw codes 42 and 43,which is the ignition module and knock sensor sensing s constant knock ( explains the low power as the timing is retarded). It changed the knock sensor, cap and rotor. Had some other weird electrical gremlins I traced to a faulty ignition switch, which was not original and was a cheap automotive part.
I then took her out again and she ran fast and strong. Until she didn't. While cruising close to WOT, I noticed the guages flicker once, then she just died. In the process tripping the helm circuit breaker ( the 15 amp breaker that is hooked to the ignition side of the ignition switch, and confirming this is all electrical). Reset the circuit breaker, and turned on the key. All the guages are down, such as the volt meter reading 10 volts (fully charged, new batteries), and the gas guage barely reading above empty with a half tank. The ignition, or exciting wire coming from the ignition switch got VERY hot before tripping the breaker again. In this condition, she would crank the engine but no fire. Then every now and then, I would turn on the key and all the guages were normal. She would fire run for just a second then die, and the guages would go down again, and trip the breaker.
I am now figuring a dead short in the ignition (purple) wire between the key and the alternator. So I start at the last connection, which is the exciting lead on the alternator. When I unplug that wire, all is normal again. Plug it in, all goes to hell. Indisconnected the alternator and again, she runs perfect. No issues at all. Plug in the alternator and it all goes to hell again.
I can't find anyone to test the alternator. This is a new, not reman, OEM Mercruiser 65 amp alternator.
So if there is a short anywhere else in the circuit, simply unplugging the alternator would not change that, right? Doesn't the short have to be in the alternator itself?
I have checked every battery and plug connection I can find and it makes no difference to the condition. The parts supplier I used to buy the alternator doesn't beleive that the alternator could be bad, but is there any other possibility? I changed the ignition module as part of this too, making no difference.
Again, the alternator is at the end of the line for the ignition/exciter wire. It is fed from th key to the alternator with some feeds off along the way. If they were shorted, it would still be shorted with the alternator unplugged, no?
Please help me understand. I can read a wiring diagram, but am NOT an electrician. Most of the wiring done by the PO is amateurish at best, and some just bad. The boat is a '98 Crownline 268.
Thanks,
Dan
This boat is new to me...
I bought it knowing it needed lots of things done. The engine is a 1998 Mercruiser 350 Mag Mpi with a Bravo 3 drive. I bought it knowing the batteries were shot. I hooked a new battery up, launched it and it ran great. I parked it in a slip and took a few weeks to fix some things, and found the alternator was bad. I replaced the alternator, which I is all I did to the engine.
I then took her out and found she was really down on power, and then stalled a few times, restarting each time. I got a suggestion that if the alternator was the only change, maybe that's thnproblem. I disconnected the alternator and she ran great but was still low on power. No stalling whatsoever. Hooked thenalternator back up and the stalling was even worse. Threw codes 42 and 43,which is the ignition module and knock sensor sensing s constant knock ( explains the low power as the timing is retarded). It changed the knock sensor, cap and rotor. Had some other weird electrical gremlins I traced to a faulty ignition switch, which was not original and was a cheap automotive part.
I then took her out again and she ran fast and strong. Until she didn't. While cruising close to WOT, I noticed the guages flicker once, then she just died. In the process tripping the helm circuit breaker ( the 15 amp breaker that is hooked to the ignition side of the ignition switch, and confirming this is all electrical). Reset the circuit breaker, and turned on the key. All the guages are down, such as the volt meter reading 10 volts (fully charged, new batteries), and the gas guage barely reading above empty with a half tank. The ignition, or exciting wire coming from the ignition switch got VERY hot before tripping the breaker again. In this condition, she would crank the engine but no fire. Then every now and then, I would turn on the key and all the guages were normal. She would fire run for just a second then die, and the guages would go down again, and trip the breaker.
I am now figuring a dead short in the ignition (purple) wire between the key and the alternator. So I start at the last connection, which is the exciting lead on the alternator. When I unplug that wire, all is normal again. Plug it in, all goes to hell. Indisconnected the alternator and again, she runs perfect. No issues at all. Plug in the alternator and it all goes to hell again.
I can't find anyone to test the alternator. This is a new, not reman, OEM Mercruiser 65 amp alternator.
So if there is a short anywhere else in the circuit, simply unplugging the alternator would not change that, right? Doesn't the short have to be in the alternator itself?
I have checked every battery and plug connection I can find and it makes no difference to the condition. The parts supplier I used to buy the alternator doesn't beleive that the alternator could be bad, but is there any other possibility? I changed the ignition module as part of this too, making no difference.
Again, the alternator is at the end of the line for the ignition/exciter wire. It is fed from th key to the alternator with some feeds off along the way. If they were shorted, it would still be shorted with the alternator unplugged, no?
Please help me understand. I can read a wiring diagram, but am NOT an electrician. Most of the wiring done by the PO is amateurish at best, and some just bad. The boat is a '98 Crownline 268.
Thanks,
Dan
