1972 johnson 125, no start this season

[starkizzle]

Hey everyone, I had this boat up and running last season thanks to a lot of help from members here so I am hoping for alil luck this year. I have a 1972 Johnson 125 electric shift that wont start. I replaced the starter and solenoid thinking that was the problem. still nothing.

So, I HAVE POWER to the top post of the solenoid, and power at the two smaller side posts when you turn the key, but no power coming from the bottom post to starter. I checked the neutral safety switch and its functioning according to my multimeter (Reads 12V when depressed, no power when in gear).
​The strange part is that while testing the leads on the solenoid and turning the key, it did crank once. So I hooked up the water and tried cranking it. It did crank for 30-45 seconds and then just died again.

​This "phantom" start was strange because after I replaced the starter and solenoid nothing was fixed. I went back out today to look at the neutral safety and check some wires, but I had been turning the key off and on several times leading up to it actually cranking. Then It stopped just as sudden as it started.
​Any advice would be greatly appreciated.

 

[jbuote]

Well I'm going to follow along on this one..
​I have a 71 50 HP Hydro-Electric, and have had similar issues...

​Went through and cleaned all connections, checked for and fixed an intermittent short in the wiring, and hadn't had an issue with it after that..
Until.... Yesterday...

​Went out to start it, and turning key to start did nothing again! Electric choke worked fine, but starter didn't do anything.. Didn't hear click of solenoid either..
​So, Started looking.. All tests with meter checked out.. Several attempts to crank it over did nothing, then suddenly... It started!!..

​So shut it off, then tried starting again... Nothing.. And, this time, it blew the inline 20amp fuse..
​So, I'm back to checking all wiring for an intermittent short, which I've done before.

​I'll be curious what yours turns out to be..

 

[oldboat1]

think I would start by cleaning the wire connections at the battery -- sandpaper bright and shiny. Maybe you already did that. Then proceed to all wires in the stating circuit, incl the key switch wiring. I follow up with some spray electrical cleaner, although that may be more of a feel good thing.

 

[RCO]

Do you have access to a factory manual? If you are getting power at both small terminals at the solenoid, that is your issue. One gets power from the start circuit on the ignition switch, the other is grounded to energize the solenoid. I don't have a diagram in front of me, but usually the ground is from the neutral switch.

 

[F_R]

No Title

Agreed. If you have 12V on both solenoid small terminals, the safety switch is not closed or is burned up.

 

[starkizzle]

Is there a test for the safety switch? I just ran my meter to it and put it in neutral with the key turned and it read 12v. I'm assuming it was good because I read 12v on that line when I neutral.

 

[jbuote]

Was doing some research and examining wiring diagram for my engine with similar issues.
​Certainly not trying to step on any toes here whatsoever. I am still relatively new, but wanted to throw this out there..

​First, you say that you get 12V when the key is turned.. Do you mean turned to normal run position or when you turn to the "Start" position?
​Unless I'm wrong, I'd imagine you would get 12V on both small starter solenoid terminals if you measured from each small terminal to ground while in "Start".. But you shouldn't in "Run"..
I think that is what they are trying to say, but in any event, if you could clarify what you mean by "when you turn the key"...

​Now to my thoughts.. lol

​I've realized that my particular issue, which is EERILY similar to yours, that it's screaming of wiring/bad connections/bad grounds..
​I've already gone through and fixed intermittent/broken wires etc..
​The one thing I have not done yet, is to clean ALL grounds..

​Having said that, I did clean all grounds that a wire is bolted to the powerhead... But what I overlooked, were the parts that are grounded through the part itself..
​Such as my safety switch, choke solenoid, temperature switch etc...
I plan on pulling those parts off, and cleaning the contact areas where they bolt on to make sure they too have a good grounding surface..
​Unfortunately, on mine, the temperature switch would require me to take the head off I believe, so I'm going to skip that one for the moment..
​I guess my point is, that just because my "Wire Grounds" were cleaned, there are other grounds that could be a problem..

​Also going to clean out my main wire harness plug with contact cleaner to be sure there's good connections there..
​
​Using the diagram F_R provided, I put a red dash-dot square around the items on your engine I believe are grounded by being bolted on..
​Those are the ones you may want to consider removing, cleaning the mating surface, and re-installing to ensure proper grounding as well..



​This is really just a thought I had, and I've yet to do it, and see if it makes a difference on my end.. Just wanted to present that as a thought...
​Perhaps the guru's here can say if I'm even close with this, but it's about all I have left that makes any sense..
​At least for my engine..

​Thanks for indulging a relative newbie here, and I am just trying to share in hopes it may help.....

 

[F_R]

Is there a test for the safety switch? I just ran my meter to it and put it in neutral with the key turned and it read 12v. I'm assuming it was good because I read 12v on that line when I neutral.

There is your test right there. (If by turn the key, you mean turn it to "start"). The safety switch should be grounded, which means there should be 0 Volts showing on your meter. The fact that it shows 12V means it is not grounded. So why is it not grounded? One of three reasons:

1. Throttle set at too-fast position. The function of the safety switch is to prevent you from starting it at fast throttle settings. Of course the remedy is simply pull the throttle back a bit.

2. Safety switch is not adjusted properly. This can prevent the switch button from being pushed in at the correct throttle settings.

3. Safety switch is defective. This is very common. They are not a very robust switch and will instantly be destroyed by improper attempts at jump-starting. Replace the switch. OK, so the alternative is ground the wire. But that defeats the function of the safety switch, so I'm not suggesting you do that.

BTW, just so you know, there is a second safety switch built into the shift switch in the remote control, which demands it be in neutral to start. But your problem at the moment is the one on the throttle on the motor. The one in the control is working, as proved by the fact that you are getting 12V to the solenoid when you turn the key.

 

[F_R]

Following up on what I just wrote, attempting to use a car solenoid will also instantly destroy the safety switch. Car solenoids are different than what belongs in there. But I don't think that's what we have here, is it?

 

[jbuote]

There is your test right there. (If by turn the key, you mean turn it to "start"). The safety switch should be grounded, which means there should be 0 Volts showing on your meter. The fact that it shows 12V means it is not grounded. So why is it not grounded? One of three reasons:

With all due (and well deserved) respect, I have to ask...
Why would the voltage read 0 if it was grounded?

​If a circuit is working properly, and is grounded, I'd expect to be able to put my red probe onto the safety switch wire, and my black probe (com/ground) to ground and see the voltage being supplied to that point. If I saw 0 volts, to me, that tells me there is no power to that point and therefore there isn't any power being supplied so the problem is before the switch I tested.

​Now if it were resistance, I'd agree.. 0 Ohms would mean it's grounded, and a resistance value could mean it isn't grounded, or there is corrosion or an issue..

​Have I missed something? :noidea:

 

[F_R]

Voltage is supplied to one small post on the solenoid. From there, it goes through the pull-in coil within the solenoid and out the other small post. Then it goes to the safety switch. Keep in mind that the pull-in coil has a specific resistance.

Aw nuts, I started to explain it scientifically, but it was getting complicated so I backspaced it out. Short version is the voltage is dropped across a resistance (the pull-in coil) according to the current through the resistance (Ohms Law).

With the safety switch closed and grounded, current flows through the circuit, resulting in a voltage drop across the pull-in coil (12V voltage drop). So you have 12V going in and 0V going out because of the drop. The energy is dissipated through the coil in the form of magnetism.

With the safety switch open and not grounded, no current flows through the circuit so there is no voltage drop across the pull-in coil. Since there is no voltage drop, it appears the same coming out (12V) as what went in (12V).

Voltage drop tests are extremely valuable in diagnosing such problems. This would especially apply when it comes to starting circuits. You can learn all about it in most any Electricity 101 book at the library. Ohms Law and resistors in series.

 

[starkizzle]

When I turn the key over, meaning trying to start the boat is when I get 12v to both small post and at the safety switch. with it just on "ON" I'm only getting power to the top of the solenoid.

 

[F_R]

When I turn the key over, meaning trying to start the boat is when I get 12v to both small post and at the safety switch. with it just on "ON" I'm only getting power to the top of the solenoid.

As I said, the safety switch is defective or not closed. To prove it, disconnect and ground the wire leading to it. I think you will find the starter will then work when you turn the key to start. Now that you have proved it, deal with that safety switch as already explained.

 

[starkizzle]

Damn I guess I misread your earlier statement. I had the function of the switch backwards in my mind. I just grounded it and she started cranking. Well that was the hard part so far boys. I wish I didn't already purchase a starter and solenoid but the starter was acting up last year anyway. Thank you guys very much, il probably be back in a couple hours when she doesn't turn over ahahahaha I hope not lol