1974 Mercury 650 starting problems

[grizzly1530]

Hi,
I have a 1974 Mercury 650 3 Cylinder that won't roll over. The previous owner had it going, but left the cover off the boat all the time, and the battery cables got bad and he tried to start it and the wires arced. Ever since then it hasn't rolled over, so he gave it to me and I put a new starter solenoid in it, but that didn't help. I ran a jumper from the postive battery terminal to the positive terminal on the starter, and it rolls over then. Somehow power isn't getting from the key to the starter. I have no idea what to do now. I tried using a test light, but don't know what wires should have power from the switch assembly when I turn the key. I don't know much about motors, and I can't find any kind of wiring diagram online. Please help!

 

[Barnacle_Bill]

Re: 1974 Mercury 650 starting problems

Yellow wire from the switch activates the solenoid. It goes thru a neutral interlock switch located in the remote so you can't start it in gear.

 

[grizzly1530]

Re: 1974 Mercury 650 starting problems

So, do I have to take the control box at the key apart? If so, how hard is it, and do I have to worry about any springs or anything popping out of place when I take it apart? I just don't want to take it to a marina, and pay out the nose for something that seems like an easy fix.

 

[FLATHEAD MAC]

Re: 1974 Mercury 650 starting problems

buddy's got a mercontrol box and just recently opened her up to check the internals, there is a little roll pin that goes between the shift cam and a little metal plate, that is your neutral detent, it will pop out. to reinstall make sure control is in neutral there is a detent in the shift cam so when you shift from forward or reverse to neutral you will fell it pop into the detent. not hard to do bur is tricky putting back. buddys box was very dry so i renoved cams cleaned and relubed, also good time to check wires inside for any electrical issues

 

[grizzly1530]

Re: 1974 Mercury 650 starting problems

I will definitely take the control box apart and make sure all the wires are good, but I don't think its in the control box. Using a test light, I am getting juice to some of the wires at the switch box assembly in the motor where all the wires come in, when I turn the key. I ordered the solenoid, and put that on, but I'm not sure if there is a positive or negative side to them? Its completely round with 2 small poles for the little wires, and 2 larger poles for the battery cables. It had no positive or negative markings on it. If I provided pictures of what I'm looking at would that help?

 

[beatlesfan]

Re: 1974 Mercury 650 starting problems

I had a similar issue with my 1971 Mercury 650. After I put in a new starter and solinoid I was still having issues. The solinoid in mine had too large post on the outsides, and two smaller ones inbetween. The large post on the solinoid facing the motor was the positive and went directly to the pos on the starter. The other large post facing away from the outboard went to to ground on the outboard. I would check the yellow positive wire for cracks/ burns. You could be losing power to the starter there. Double check and clean all connections. Pictures would help.

 

[merc850]

Re: 1974 Mercury 650 starting problems

Here's the wiring for the solenoid is only a heavy duty switch and is not polarized. I wouldn't pull the Mercontrol apart until you've checked the switch operation with a voltmeter.

 

[grizzly1530]

Re: 1974 Mercury 650 starting problems

Thank you all for your help! I haven't had a chance to work on it much this week due to Mandatory Overtime at work, but I am going to try a little bit tonight. I will let you guys know what it was if I get it fixed tonight!

 

[grizzly1530]

Re: 1974 Mercury 650 starting problems

Hi All. I got a chance to finally work on it this weekend (stupid winter months). I still cannot figure this thing out. I'm almost certain its something in the control that is doing this. When looking at the wiring diagram on this thread, I have power at all times with the red wire straight to the solenoid, but I have nothing from the yellow wire, or "B." Should I have power from this, and would this most likely be from the control box?

 

[merc850]

Re: 1974 Mercury 650 starting problems

The "B" wire is + power from the key, you have to turn the key and see if there's 12v to ground and the throttle handle has to be in neutral. As a test if you jump from the red wire to the little yellow wire on the solenoid the starter should turn over.

 

[timmeraw]

Re: 1974 Mercury 650 starting problems

Here is the correct wiring diagram for your 3 cyl Merc 650 - Distributor Ignition without Points.

http://www.maxrules.com/oldmercs/Wiring/1966ona/29.jpg

I am working on the same motor (72 650) with no spark issue so I am getting to know the wiring really well.

 

[grizzly1530]

Re: 1974 Mercury 650 starting problems

I've spent a few hours on this, checked all the wires, and they are in surprisingly good condition. Could it be the ignition switch? I feel like a real dumb a** asking all these questions, but all the marinas in the area told me. "With old engines, we just try stuff until it works." That could work fine, or cost me WAY too much money. So I am trying to do everything possible myself. Thanks for all of your help everyone!

 

[Treker57]

Re: 1974 Mercury 650 starting problems

Hope you figure it out, thats really a **** poor thing for a marina to say--"With old engines, we just try stuff until it works." sounds like going grocery shopping at Auto Zone

 

[grizzly1530]

Re: 1974 Mercury 650 starting problems

Yeah, for some reason, around this area, everyone just goes and gets new stuff. There aren't many marine mechanics that service older motors. There also aren't many people around here that do it as a side business, so I'm kind of left on my own. I went out fishing with my little guy this weekend, and these next few days are gonna be in the 40's for temp, so hopefully I get a chance to work on it. Its getting really frustrating though, thats for sure.

 

[grizzly1530]

Re: 1974 Mercury 650 starting problems

Hey everyone, just thought I'd update. I finally had some time to work on it, checked the wiring at the controls, and they all had juice like they should. Then I was messing around with the wire going to the neutral switch, and low and behold, it started!!!! So, tonight, I am going to clean up that area, and replace that wire. I just want to thank everyone for their help! It was very much appreciated! I definitely couldn't have done near what I did without you guys. I even impressed my dad, who went to school at one time to be an outboard mechanic! Thanks guys!!!!!