Hello - just joined the forum so hopefully someone can help.* I have a 1996 Sea Ray 190 with a 5.7L Mercruiser (carb) with Thunderbolt V ignition.** It ran fine all last year, and when I last took it out in December (Sunny San Diego).* It sat under boat cover but suffered several very rainy days since last used.*Inside of boat was damp, but no reason to think I got watter in distributor*or anything like that.
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On my checkout run a couple of weeks ago, about 20 minutes in I noticed my voltmeter was low - around 10.5V.* I revved the motor and the volts jumed to 14.5, so I settled it back to idel and the voltage stayed at 14.5 (at idle).* The motor would idle fine and the system would charge at ~14.5V, but when I then tried revving the motor, voltage would drop as speed increased, until eventually the motor sputtered and died. The only other thing I noted out of the ordinary was that the tach was reading ~300rpm with the motor and key off.* It seemed to read correctly at speed, but never returns to zero.*
*
Brought the boat*home, tested the batteries, and battery connections (all ok), and then yanked the alternator (having convinced myself it was a voltage regulator issue).* Needless to say, I have a nice new alternator, and the same old problem.* Pulled the 12V feed to the starter (which is where battery, alternator and starter connect) and cleaned and tightened (it was already clean and tight).
*
Tonight, I followed the Clymer manual's advice, and confirmed (1) grey lead on tach was not grounded, reading ~12v, and removing the grey tach lead from the coil did not return the gauge to zero, (2) both sides of the coil read roughly 12v (3) the alternator output (orange wire) reads the same as the active battery, and roughly ~0.5v more than the reading at the dash voltmeter, (3) reistance between the positive side of coil and high tension (output) is ~10,500 ohms (manual says should be 7500-8500).
*
So in a nutshell, the motor runs rough, sputters, and trying to rev it usually causes voltage to drop and the engine to die.* It will readily start each time, but won't run smoothly or rev, and the voltage meter registers changes in voltage each time.*
*
I'm planning to do the following, as my last ditch effort:* remove all leads to the tach, in case it was shorting out the coil just enough to drop the voltage as coil firings increased.* Only reason I suspect the coil/tach is because of the false reading.* Apart from that, I'm not sure what else to do.* The advice I've seen is "check every connection" which is a bit useless as advice since there are hundred of connections, and no way I can be sure I can even see all of them.
*
Anyone have similar experience, or suggestions?* Could a short in the knock sensor, electric choke, shift interrupt switch, slave solenoid, or IC module cause these types of problems?
*
Thanks in advance - Jurisd
*
On my checkout run a couple of weeks ago, about 20 minutes in I noticed my voltmeter was low - around 10.5V.* I revved the motor and the volts jumed to 14.5, so I settled it back to idel and the voltage stayed at 14.5 (at idle).* The motor would idle fine and the system would charge at ~14.5V, but when I then tried revving the motor, voltage would drop as speed increased, until eventually the motor sputtered and died. The only other thing I noted out of the ordinary was that the tach was reading ~300rpm with the motor and key off.* It seemed to read correctly at speed, but never returns to zero.*
*
Brought the boat*home, tested the batteries, and battery connections (all ok), and then yanked the alternator (having convinced myself it was a voltage regulator issue).* Needless to say, I have a nice new alternator, and the same old problem.* Pulled the 12V feed to the starter (which is where battery, alternator and starter connect) and cleaned and tightened (it was already clean and tight).
*
Tonight, I followed the Clymer manual's advice, and confirmed (1) grey lead on tach was not grounded, reading ~12v, and removing the grey tach lead from the coil did not return the gauge to zero, (2) both sides of the coil read roughly 12v (3) the alternator output (orange wire) reads the same as the active battery, and roughly ~0.5v more than the reading at the dash voltmeter, (3) reistance between the positive side of coil and high tension (output) is ~10,500 ohms (manual says should be 7500-8500).
*
So in a nutshell, the motor runs rough, sputters, and trying to rev it usually causes voltage to drop and the engine to die.* It will readily start each time, but won't run smoothly or rev, and the voltage meter registers changes in voltage each time.*
*
I'm planning to do the following, as my last ditch effort:* remove all leads to the tach, in case it was shorting out the coil just enough to drop the voltage as coil firings increased.* Only reason I suspect the coil/tach is because of the false reading.* Apart from that, I'm not sure what else to do.* The advice I've seen is "check every connection" which is a bit useless as advice since there are hundred of connections, and no way I can be sure I can even see all of them.
*
Anyone have similar experience, or suggestions?* Could a short in the knock sensor, electric choke, shift interrupt switch, slave solenoid, or IC module cause these types of problems?
*
Thanks in advance - Jurisd