2000 Mercury 125 ELPTO electrical system unresponsive

[Toolman137]

I have a 2000 Mercury 125 ELPTO Serial # OTOXXX. While getting ready to leave on a fishing trip, I tested the motor in the driveway to make sure it would run. When I turned the key, the motor turned over for about two seconds and then everything went dead. There was no pop or backfire or any sound of something breaking. When I tried to turn the key again, there was no response. The engine wouldn't turn over, there was no click to be heard when you pushed in the electric choke...nothing. Also, whatever happened also disabled my power tilt / trim. I've checked all of the trim switches, and none will respond. I checked / replaced the fuse on the top starboard side of the engine block and the fuses on the dash panel... they appeard fine. I replaced the battery terminals on the wires leading from the battery to the motor. The battery is fully charged and less than 6 months old. Still same effect. I replaced the ignition switch on the dash thinking that might be the problem...no effect. When I made my garage completely silent and tried the motor tilt... I could barely hear a faint electrical crackling sound coming from somewhere on the starboard side of the engine block. Any ideas? All of the nav lights and other electrical accessories work just fine. It seems to be only the motor that is effected. Any help would be appreciated. Thanks

 

[CharlieB]

Re: 2000 Mercury 125 ELPTO electrical system unresponsive

Crackling sounds are NOT GOOD, that is a very poor electrical connection frying!

Disconnect the battery cables from the battery then remove the electrical cover on the side of the motor to inspect BOTH battery cable connection to the engine block and to the starter relay. This is where power comes off to the trim motor and thru the fuse to the ignition switch.

Is the cable end and post burnt? Anything else?

If you are very lucky you can sand terminals clean, re-tighten, reconnect the battery then retest.

If much more is burnt to bad you may need to replace parts.

Repost your finding, pictures could also help.

 

[Toolman137]

Re: 2000 Mercury 125 ELPTO electrical system unresponsive

It was very difficult to tell whether the terminals were burnt due to the fact that the previous owner had apparently painted ALL of the terminals with what appeared to be some type of black anti-corrosion compound. I DID, however, notice a small wire that went from the small righthand terminal of the starter solenoid to the ground / mounting bolt on top of the solenoid had a small bit of bubbled insulation ( I assume from high heat in the wire, but that's just a guess ). I replaced the battery terminals and then checked for power at the point where the cables terminate into the engine block. Red terminated into the lower large post on the starter solenoid. Black onto a grounding stud below the starter motor with about three other ground wires.

As a precaution, I replaced the starter solenoid and took a palm sander to every wire connection that previously had that corrosion stuff on it. No connection was re-attached until it shined. Did that to every grounding stud / bolt I could find. Still no effect.

I do know after using a multimeter that I am getting power ( full battery - 12V ) from the battery to the starter solenoid. I hooked up the multimeter to the output wire from the starter solenoid to the starter motor and turned the ignition key. Nothing. Not even a tremble on the meter. I am beginning to suspect that somewhere inside of the bowels of the boat there is a burned out wire running to the ignition switch that is not letting me get power from the switch to the motor.

I am posting photos of the new starter solenoid, the starter motor, and the electrical connections on the starboard side of the motor. If you see something I've missed, please tell me.... as this is about to drive me nuts.

 

[mercfixer]

Re: 2000 Mercury 125 ELPTO electrical system unresponsive

You may need to find someone with a test harness.......that way you can eliminate the wiring harness from the keyswitch to the outboard.......you can most likely hear the crack'lin if you can be nearer to the source.....
just a thought....

 

[CharlieB]

Re: 2000 Mercury 125 ELPTO electrical system unresponsive

Check the fuse that is immediately above the relay, do not trust just looking at it, take it out and check it with your Ohm's Meter, also check the socket, one side should be hot coming directly off of the battery post on the relay.

Next, pull apart the Cannon Plug, that big plug in the wire harness that connects the motor wiring harness to the main harness to the controls. The two fatter pins are the main power lead and ground, a poor connection here will also cause everything to fail.

If the fit is too loose you can use an X-acto knife, carefully slide it into the slot of the male pin to widen it JUST a hair.

 

[Toolman137]

Re: 2000 Mercury 125 ELPTO electrical system unresponsive

Found the culprit.... Found a splice in both the positive and negative cables deep inside of the hull of the boat... Apparently the previous owner had a problem in the cables and instead of replacing the cables, he decided to cut the cables in half and put a rigged up splice in both lines... I had to pull the cables out from the bowels of the boat to find it... When I took them apart to inspect them, they were a real mess... That explains why I had 12v at the solenoid one minute, but when you jiggled the wire, the power would die... When I first began troubleshooting the engine, I put a meter on the wire and it showed power. But when I moved the wire back into position and tried the key, apparently the bad splice disconnected again and power was lost. I only caught the problem when I started retracing my steps again to see what I had missed. I installed the NEW cables and the engine fired right up... Trim works better too... I only wish I had discovered this 5 days ago.... Thanks for the help guys.