88 Merc 100hp Electrical issues

[88sevilleOB]

Stumped by my 1988 Searay Seville OB with the 100hp Mercury. Everything is in great condition but after running it for 1 to 10 minutes the tach flickers and all gauges go dead. Sometimes I can restore things by pushing the trim or blowing the horn. A few minutes later they will go dead again. Occasionally the trim will stop working and if I shut off the motor it
will not turn over when I try to restart it. I have cleaned all of the conn3ctions in the motor and
installed a new starter solenoid with no luck. A local mechanic had it four a month but gave up. Any ideas or suggestions would be greatly appreciated.

 

[Dave1027]

I have the same boat.
Sounds like you have an intermittent connection. What about the main battery cable to the battery? Maybe the key switch? I would put a volt meter on the 12 volt line in the gauge cluster and start pushing on all wiring till you see a deflection.

 

[88sevilleOB]

Thanks for your reply. I have a new battery @ 12.62 volts. I used jumper cables to “bypass” the main battery cables with no luck. I will try your suggestion asap. Also thinking about running a secondary ground wire from the motor to the instrument cluster.

 

[QBhoy]

Thanks for your reply. I have a new battery @ 12.62 volts. I used jumper cables to “bypass” the main battery cables with no luck. I will try your suggestion asap. Also thinking about running a secondary ground wire from the motor to the instrument cluster.

Is that the Volts when running ? Likely not…sounds like a stator or rectifier issue, if not a battery issue.

 

[88sevilleOB]

Voltage when running increases from 13.0 at start to 14.2 at cruise. We have noticed that the voltage shown on the dashboard gauge is lower than the actual voltage at the battery per a voltmeter.

 

[Dave1027]

Thanks for your reply. I have a new battery @ 12.62 volts. I used jumper cables to “bypass” the main battery cables with no luck. I will try your suggestion asap. Also thinking about running a secondary ground wire from the motor to the instrument cluster.

I would take a resistance reading from motor ground to the ground at the cluster. Then also watch the reading while moving the wiring, looking for deflection.