Mercury 850 outboard wont turn over at times

[udusted]

Hello,

I have been having an issue on the water and I can't seem to figure it out and hopefully with your advice I can get my boat up and running. I have a 1976 Glastron T166 Xl with a Mercury 850 outboard. I am having issues with the my boat turning over. At times I have power other times nothing. This only seems to be the issue on the water and have never had the issue when running it on land with the muffs. I don't know a lot about boats and learning more everyday. I have tested the neutral safety switch and this seems to be working fine. I also cleaned and used dielectric grease on the battery connections. When I turn the key over at times on the water I hear nothing not even the choke engaging. I open up the cover and see the starter and the starter solenoid is there anyway to trouble shoot those to items. Also is there a way to trouble shoot the pin connection on the side of the motor where the boat wires go to it? How do you open that connection does it just pop off. Also is there a way to trouble shoot the wire inside the boat connection that runs to the MerControl throttle box? I am running out of ideas and look forward to any feedback. Thanks

 

[Jacobsele]

I'd check the ground connections on the motor, clean them up with a wire brush. It could be the solenoid also but don't really sound like it (they are cheap, around $20). I'm still newer to boat motors so I could be totally wrong. Good luck.

 

[hotrod53]

If your key is ON and you press the choke and nothing happens, it's not the solenoid or the starter. You are losing power from the control box to the motor. The plug on the side of the motor just pulls off, I would start there. Clean the contacts real good, put some dialectric grease on it and try it.

Turning the key ON without starting the motor is independent of the starter and the solenoid. I think I would have someone hold down the choke button and wiggle the plug on the motor. When you try and start the motor, you are putting 12v on the small solenoid wire to close the solenoid and transfer big power and big current to the starter. If you ever get in a jam, you can short a screwdriver across the solenoid to engage the starter but if you lost 12v to the motor, it won't keep running anyway.

Take a look at your wiring from the plug to to the motor inside of the power head enclosure. Those wires dry out, crack, and break if you're motor is from the 70s or 80s. Are you losing power to your lights at the same time, assuming your lights run off of the starter battery? How about the main power wire on the battery as it goes into the terminal and not on the battery itself? You can have a good connection at the battery terminal but a bad connection from the cable to the terminal.

 

[udusted]

Thanks fr all your help on this and will try and pull off the connector and use the grease and start there. I also like your idea with the choke and wiggle the wire. My fish finder doesn't shut off but is ran straight to the battery. I do however now that you mention it see the rpm's shoot down to zero sporadically and then back to normal. I did also notice on my last time out I tried to see if I had 12v at the starter solenoid and nothing. I did move the trim all the way up then down and it then would turn over. Is the control box the throttle box? I think you might be right with the power cable from the motor to the control box. So the wire harness that plugs into the motor that is about the size of a half-dollar and is round just unplugs? I think I tried pulling on that and didn't want to come off and didn't want to break it so I left it be. Thanks again for all your help. I am pretty new to having a big boat and learning more everyday

 

[udusted]

I also cleaned the battery cables up with wire brush baking soda and then used dielectric grease and same issue thanks for your help too Jacob

 

[udusted]

I found out what the issue is I have a broken power or ground wire in the harness about 6 inches from the motor connector. The wire must have broke when sitting in the wire harness hook and turned steering wheel to far or something. Thanks for all your help. Now I need to either find a new wire harness or try and fix this one. I am thinking ill cut open both positive and negative wire casing to see if in fact broken wire and solder together. I have 2 feet of extra cable sitting in the back of the boat its too bad the connector for motor comes off and could cut wire and re attach....Any suggestions on the best way to fix this?

 

[Jhoppy]

You could use an ohm meter to test your wiring harness, unhook the wiring at both ends and test continuity while wigging the wires. As already mentioned the wiring and insulation from that era of motor has gotten brittle, you could cut and splice the wires or run a new wire for the one that is broke. On my 1971 i compleatly removed the factory wiring, mounted a terminal strip in the motor housing, made a new motor wiring harness for the motor, and used a newer boat wiring harness made to work with a terminal strip. As far as finding a new wiring harness your not likely to find one in good shape due to the age.

 

[udusted]

I found out what the issue is its with the ground in the wire harness. I think its behind the plug that goes to the motor. I cut about 6 inches back from where it binds on the hook and assumed it would be here but the wire is fine. So I am assuming its the connection in the plug. I also since playing around with this found on my RPM gauge isn't working