Basic Electric Problem (1990 OMC 4.3L)

[andrewgroup]

Yesterday I experienced a problem I would like some basic ideas for troubleshooting. After boating a short bit the dash panel and engine start appeared to dead. I found the large nut retaining the battery cable was finger loose. We tightened this boat and used a budy battery jumper to start the boat. When I engaged the switch to raise the outdrive it nearly killed the engine. After running 30 minutes at the ramp the engine would not restart on it's own and outdrive would not raise.<br /><br />I charged the battery, and added a second battery option to the boat to prevent this in the future. meanwhile, with two known good batteries, when I turn the ignition switch to on, the dash guages still appear dead and the starter is silent.<br /><br />I did see the gauges move once and I suspicious that I have an intermittent electrical trouble. It's a 1990 Mariah 1850XL with a ton of gauges.<br /><br />I'm pretty technical about wiring and I've looked at the Clymer 86-93 OMC shop manual and the electrical diagrams seem slightly different from my observations...<br /><br />Could someone tell me what the assist solenoid is and where it might be and what it is used for..<br /><br />Any other tips to diagnose this trouble would be appreciated...

 

[boat doc]

Re: Basic Electric Problem (1990 OMC 4.3L)

clean those battery connections real good, make sure that the where the cables go into the termanals are good and tight. I have also seen battery switches fail, they have a spring in them that get week, causing bad connection. Turn the key to the ignition position (right before you start), and start wiggleing battery cables and see if your dash comes to life. I have also seen the cannon connectors get coroded (the big round connection that plugs up at the engine). pull that in and out a few times, see if that brings your dash to life. If that was the problem get you some di-electric grease, and grease that booger up.

 

[Boatin Bob]

Re: Basic Electric Problem (1990 OMC 4.3L)

IF you are still dead you should check the 2 big 50 amp glass fuses. One supplies power to the slave solenoid plus feed the dash, the other one is for the trim/tilt motor, if you had bad connections you may have caused overcurrent and blown one or both of those fuses. They are on the engine usually near the back in black rubber inline fuse holders.

 

[andrewgroup]

Re: Basic Electric Problem (1990 OMC 4.3L)

OK, That was good advice. I started with my volt/ohm meter and measured voltages at the starter solenoid and then at both sides of the 50 amp fuses.. 12Volts everywhere. At first this confused me until I remembered some of that ohms law stuff. Mainly V=IR. IF the resistance from the battery terminal was say 10k ohm and the ciruits where all open, then the entire 12volts would be seen everywhere until a load was put on the ciruit. Since the resistance might be extremely high then any load would likely not get any amount of current to operate. This lead me to take your advice.<br /><br />I removed both battery terminals and disassembled the clamps holding wire to the terminals. (Aftermarket) yuk. Despite looking very good on the outside the bed where the wires laid in and the metal clamp over the wires were in terrrible shape.<br /><br />A little work with the small wire brush attached to the dremel tool made this look new. All appears to be well.