1975 70 HP Johnson won't start

[hummer5]

Re: Johnson model 70ESL75B. During the past couple of boating seasons, I often had difficulty starting the motor. Only after moving the start-up lever up and down rapidly several times the engine would then start. Several days ago I had the same problem and after moving the start-up lever the motor started. After a short boat ride, I docked and stopped and restarted the motor 3 times without any problem. Several hours later when I again went to start the motor, it would not turn over even after moving the start-up lever, which I think was just coincidence in the past. All efforts to start the motor failed. The battery is almost new. The lights and horn work. The choke solenoid also works. The various mechanisms on the motor appear to work when I move the throttle lever and start lever on the control box. I used jumper cables direct from the battery to the starter and it seems to crank okay. I partially disassembled the control box and stuck a flat blade screwdriver between the neutral safety switch and the throttle lever to see if the problem could be there, but still no luck. I checked all visible wiring on the motor and it appears to be okay. Could someone please offer me some suggestions or assistance in diagnosing and repairing the problem. Thanks for your help.

 

[tashasdaddy]

Re: 1975 70 HP Johnson won't start

sound like a bad connection in the neutral safety switch, or a break in the wire. if you still have the control box open, use a jumper with 2 aligator clips, on each post of the neutral switch.. and try to turn it over.

 

[OBJ]

Re: 1975 70 HP Johnson won't start

Hi hummer...welcome to iboats!

The choke solenoid is working...good...but did you pull the front cover and make sure the choke plates were closing? Seems, from your post, that once you get it running, it "seems" to start OK....in rapid successsion.

Working the start up lever up and down is opening and closing the throttle plates...trying to suck in fuel. Once the fuel gets into the engine, it fires.

I think I would start at the fuel tank. Make sure the primer bulb is firm when priming before start up. Again, make sure the choke plates are closing.

If nothing elese...take a spray bottle of premix and give each carb a squirt before starting. If it fires off, you have a fuel flow problem.

Do you know when the last time the carbs were overhauled and the fuel lines renewed? Hard fuel lines can leak air at connection points.

 

[tashasdaddy]

Re: 1975 70 HP Johnson won't start

have you tried taking jumper cables, pos side of battery to pos post on starter. if that works, turn the key and see if it will start like that. if it does it's the starter solenoid. alson have you cleaned every connection between the battery and starter, and soleniod. this will keep it from turning over also.

 

[hummer5]

Re: 1975 70 HP Johnson won't start

have you tried taking jumper cables, pos side of battery to pos post on starter. if that works, turn the key and see if it will start like that. if it does it's the starter solenoid. alson have you cleaned every connection between the battery and starter, and soleniod. this will keep it from turning over also.

 

[hummer5]

Re: 1975 70 HP Johnson won't start

Yes, I did use jumper cables as you suggested and the starter did turn and crank the motor. I did not actually start the motor because I was performing my diagnostics in the boathouse (out of water) with the spark plugs removed so did not want to actually start the motor for obvious reasons. According to your diagnosis, this then suggests a starter solenoid problem. Since outboard motors are somewhat foreign to me, but I like learning, where is this solenoid located? Mounted on the engine somewhere near the starter? If so, whereabouts in the electrical wiring that leads to the starter? Thanks greatly.

 

[tashasdaddy]

Re: 1975 70 HP Johnson won't start

if you follow the wire from the positive post on starter it wiil lead you to the starter solenoid,,the solenoid has 4 connections, 2 large and 2 small..pay close attention to where the wires go. easy to change remove cables form battery, 4 wiring connections and 2 screws.

 

[Walker]

Re: 1975 70 HP Johnson won't start

Well, your starter works when directly jumped so start diagnosing your way forward towards the key switch. Put a voltmeter on the starting circuit post of the solenoid and see if and how much voltage you get when you turn the key. If your getting 12 or more volts and the starter still does nothing then you solenoid is bad. If you get low or no voltage then you have a bad wiring, or bad neutral switch or bad key switch. You can test the neutral switch for continuity with a multimeter. You can test the key switch with one too,

 

[tashasdaddy]

Re: 1975 70 HP Johnson won't start

agree with walker , if it is the solenoid the original part # is 0383622 i'm sure it has been superceed

 

[rickdb1boat]

Re: 1975 70 HP Johnson won't start

As TD suggested, first thing to do is check all connections to make sure they are tight and clean. Both battery terminals and at the engine ground and selenoid connection....Take them all off and clean them until shiny...

 

[OBJ]

Re: 1975 70 HP Johnson won't start

Did I read the original post wrong or what......LOL! Are we dealing with an engine that won't start or it won't crank??

I'm confused.....again......d

 

[tashasdaddy]

Re: 1975 70 HP Johnson won't start

obj, i read it as won't turn over, crank.

 

[OBJ]

Re: 1975 70 HP Johnson won't start

Thanks TD.....re-read it a couple times.....guess it's hard to start when it cranks but then it stopped cranking.....OK....got it now....I hope....LOL....OH Sunday morning....

 

[tschamp20]

Re: 1975 70 HP Johnson won't start

have you tried messing w/ throttle lever in motor.the safety switch on mine has to be just right in order to crank.have somebody turn the key while you barely move the throttle lever,may need to be adjusted.but what do i know.worth a shot!

 

[hummer5]

Re: 1975 70 HP Johnson won't start

have you tried messing w/ throttle lever in motor.the safety switch on mine has to be just right in order to crank.have somebody turn the key while you barely move the throttle lever,may need to be adjusted.but what do i know.worth a shot!

 

[hummer5]

Re: 1975 70 HP Johnson won't start

Will give that a try before performing various other tests suggested by others. This is one awesome forum. Will certainly suggest/recommend this forum to others who have outboard problems or issues.