Logo
FULL SITE MENU

Shift Interrupter Switch Issue

S

Stackfish

New member
I have a 1996 Johnson 150hp motor that will not run past 3000 rpms. I've just had the powerpack replaced and I now suspect an issue with the shift interrupter switch. From everything I've read, my understanding is that when the shift interrupter switch is depressed (circuit closed) the motor will run on only 3 cylinders. My motor is the exact opposite, it will only run on 6 cylinders when the switch is closed.

To confirm this, i've pulled the ground off of the switch and the motor was stuck in 3 cylinder mode. I've also had the motor bulking at 3000 rpms and closed the switch with my hand (with the ground re-connected), and the motor smooths right out. Can someone tell me 1) If the motor should run on six cylinders with the switch open and 2) assuming mine is working wrong, could my switch interrupter wires be crossed?

Thanks in advance
 
The shift interuptor switch effected the fire on #1,3, & 5 only. It makes it easier for you to get the engine out of gear by making the engine run rough for a few second. I do not know of a way it can be wired backwards.
It is possible that your motor is in SLOW. That limits the RPM to 2800, but I don't see where the switch would help,it run on 6? Just trying to give you some ideas. You don't have to have a horn or overheat to be in SLOW.
Does the engine have Champion QL78YC spark plugs in it? Must have to run properly. It's an ignition interference thing.
To disconnect the interuptor switch completely you need to unplug the black/yellow stripe wire in plug up by the regulator/rectifier. Some have two wires & some three with the ground. If you run motor this way motor may be harder to get/shift out of gear.
Give us your results?
 
Either the switch is working or it aint. I doubt it is working backwards can you adjust the switch in neutral so all six are firing? Can you post a wiring diagram would be helpful?
 
Plugs and Pack are correct. With respect to Limp mode, the boat was having occasional limp mode issues that's why I had the PP replaced. When it appeared to be in limp mode it would start to shake at 2500 on the nose. Now with the new PP it bulking at around 3000 rpm.

With respect to the switch working backwards, my motor runs fine when I close the switch, and appears to be on 3 cylinders when the the switch is open. If I take the ground off of the switch the motor won't do more than 3000, but if I reinstall the switch ground and close it by hand, the motor runs normal.

There are two plugs on top of the motor where the switch is connected. I pulled one and it was a single pole connection, when I get to the boat again I'm going to pull the other to see if its also a single pole connection. I'm thinking maybe these two are crossed.
 
Here's where I'm at with this issue. 1) The wires cannot be crossed where the switch attaches to the wiring harness since 1 plug is male and the other is female. 2) I swapped out the interrupter switch with another switch and the problem persists. The only thing I noticed is that the female plug on the wiring harness is corroded and that part of the circuit may not be complete (I'm going to try and guarantee this connection on my next trip to see if this is the issue).

My mechanics are stumped on this one, does anyone have a theory as too why my interrupter switch seems to be working backwards? Again my motor bulks at 3000 rpm but purrs as soon as I manually close the interrupter switch with my hand.
 
My thought is how it is adjusted. It sounds like there would be two detents on the shift lever between f and n and between r and n can you adjust the switch to run on all cylinders in neutral? It has something to do with how itis indexed do you have pics of it in neutral?
 
The key point that I need clarification on is how it's supposed to work with respect to the switch position. From what I've seen on the internet and heard from my mechanics is that when the switch is CLOSED the motor is in 3 cylinder mode.

If that is true, there is an electrical issue with my motor since my motor is in 3 cylinder mode when the switch is OPEN and is in 6 cylinder mode when it's CLOSED. If my motor is working as designed with respect to the switch position vs mode, then I agree its a linkage adjustment issue.

Can someone verify the when the motor should be in 3 cylinder mode with respect to the switch position?
 
A interuptor only enguages when you are shifting into and out of gear. It should be running on all cylinders in neutral and in gear. Is the switch normally open or normally closed? Are you assuming or did you check with a ohm meter? My guess is it was taken apart and not assembled properly. You said you had another switch did you pull it off the other motor? Something is not right here just disable the switch and see how well it shifts with all cylinders running?
 
That some wild guess's posted....The switch is OPEN and goes closed when shifting but just or a second the goes OPEN till a shift event occurs again. I am going to say it a miswired pack. Hey T2 didn't you have a 90 degree at your house that was acting like this??? I think we swapped the blocking diode on it.
 
You are right Faztbullet, but the system is wired in different with the black/yellow connectors in the old motors both male to female connectors. That can't be done here unless someone has gone way out of there way to screw someone up? (Correct me if I'm wrong. I'm getting old & forget these days!) There is no adjusting of the switch. It is a momentary actuation upon load. Only coming out of gear. That being said IF the gearcase was hard to shift (like metal in it or shift rod binding) it could screw with the switch trying to activate. The only problem with this explanation is its the opposite of what he is telling us. His motor runs BETTER with switch activated. Makes no sense. Not doubting you, just not coming up with anything at the moment. It is a really simple system. I have seen moisture get in the switch, but results in cylinders staying cut out. Disconnect the switch & all is fine. Therefore replace switch. I can not think of a reason why activating the switch would make the engine run on 6 cylinders? I'm thinking on it.
 
Is it possible the spring is not pushing the slider back out all the way? Take the shift switch bracket apart and check the spring is in good shape andthen clean it good and use a marine lithium grease for the slider to push the slider up to open the switch. Could be the spring is just bad?
 
Thanks T2 and Faztbullet for your input this is a tough one! Here's how the switch is ohming. From the male plug to the ground, it's an open circuit until the switch is depressed then it goes to 0 ohms. From the female plug to ground it's an open circuit until the switch is depressed and then it's reading about 50 ohms (my meter is set to Rx1)

Here are some questions

1) With a 96 Johnson 150, could my PP be installed incorrectly to produce this issue?

2) What are the odds that my brand new PP is defective?

3) There is some corrosion on the female plug on the wiring harness. If the male connector on the switch did not connect with the female connector on the harness, could that cause the switch to work backwards (ie. must be closed for 6 cylinders)?

4) Where do the black and yellow wires on the harness go? Could they be mis-wired to the PP?

Thanks for your help!
 
Last edited:
@kimcrwbr I've done my testing with the switch out of it's cradle, so I'm sure that the motor runs OK with the switch depressed and poorly when it's open. Thanks for your help!
 
faztbullet said:
Was the pack replaced a CDI brand ????
Click to expand...
I've noticed posts before about CDI quality issues. Sounds like the problem here. A switch is a switch, open or closed. That 50 ohms may be some corrosion, but disconnecting the switch should allow the motor to run on all cylinders. As stated, the switch is normally open, closing when the shift lever moves from reverse to neutral to cut out one bank momentarily.
 
If all you did was replace pack my bet is pack especially if a CDI brand. If you been playing with wiring its possible.
 
Here's an update. I misspoke about the PP, my mechanic said it was from Johnson and could have been made by CDI. I went down to the boat and used a tiny drill bit to ensure a good connection between the female plug on the wiring harness and the male on the switch. It did not solve the problem but as I wiggled the drill bit to make sure I had a good connection I touched ground and got a zap from the bit. It felt like a coil zap and I'm wondering if anyone knows if that's normal?

My mechanic has asked me to start the motor and pull the plug near the starter with tan wires. He said if that fixes it he thinks there is a short in the boat. BTW he did just rig a 36 volt trolling motor, a talon, and move my bow lights. Hmm...

In case if anyone is wondering why I'm doing this and not my mechanic its because he doesn't do dock calls and I'm trying to avoid pulling the boat.
 
Here's the latest, I got my mechanic to come down to the boat and it turns out that my shift interrupter switch is working correctly. When I was testing it at the dock it was hitting the rev limiter since I was in neutral and when I depressed the interrupter switch, going to 3 cylinders actually made the motor smooth out.

The mechanic and I took the boat out and it still could not get on plane so we installed my old PP on the water. With my old PP the boat ran fine,
so it appears that the new PP is bad. Also during the trip the mechanic noticed that the switch that signals neutral was falling apart so we hardwired since we thought maybe that was the root cause of the slow mode issue since it could have been signaling that the boat was in neutral thereby kicking in the rev limiter.


Today I took the boat out and it ran great for a while but eventually started going into slow mode again. Sometimes today I would here a fast beep when I turned the key on, other times I would just get a random beep while running. At the end of today's trip the boat was stuck in slow mode, so I'm back a square one. On the water today while stuck in slow mode I

1) Disconnected the temperature sensors
2) Disconnected the oil sender sensor
3) Disconnected the big red plug (the one that when disconnected prevents the key from killing the motor

None of these corrected the problem. So my next steps are:

1) Get another PP and see if that resolved the issue.
2) Replace the blocking diode (if this motor has one)

Does anyone know if the 96 Johnson has a blocking diode?
 
Yes it has a diode in the wiring harness. Item #15 if you look at wiring harness on this site. Don't guess we would have ever figured you were reving engine in neutral that high. Some thing we just don't think about that customers can do? DUH!
During the time you were trouble experiencing SLOW did you shut the motor off? That resets the system. The motor will stay in SLOW once activated unless you turn off & restart. Just an idea.
With all of the sensors unplugged I think you may have found your old OMC pack has a problem too? Not that abnormal. CDI does build BRP/OMC pack as of late, but not originally.
It is possible that you have some deposits built up in the heads (lime here in TN). It causes errant hot horns & of course SLOW, but that can't happen with sensors unplugged. If you were to suspect that when back together you would have to pull the heads & fill them with Lime a Way, CLR, favorite deposit remover. Let sit for 24 & rinse. The nice thing is you don't have to buy head gaskets.
 
@t2stroke, thanks for your input. Sorry about the red herring with the interrupter switch, I'm just a fisherman playing outboard mechanic on the internet :) Yes I restarted numerous times since in the past that would eventually fix the issue.

Should I try replacing the diode before the PP since the PP is $$$. I'm also suspicious of a short on the engine since 1) the problem happens intermittently, 2) my PP is is a CDI dated 2016 and a brand new one has the same issue. 3) The problem once again started when I trimmed the motor (gravity/motion and wires?) while running.

As an aside, when I bought the boat in late 2017 the previous owner said he never ran the boat fast since he was running a trot line for crabs. I'm guessing the problem started with him and he replaced the PP and it didn't fix it so he just dumped the boat at a very good price so he could get a better boat for crabbing. Just a theory!

Thanks for your help!
 
Last edited:
A diode can be tested. Just a device that lets voltage past one way, but not the other. Any of the brown leads (except the temp senders) should test that way. The diode keeps any of the other systems from putting the motor into SLOW. Just overheat. The blocking diode is kinda a pain to replace! You have to dig into the wire harness. Normally doesnt give too much problem.
No problem on being inexperienced trouble shooting. That's why we are here.
 
Here's an update, I've replaced the plug wires, checked the coils for any damage and checked the routing of the tan wires wires with respect to the plug wires without any improvement. Tech support from CDI suggested pulling the plug (the one with the tan wire) from the PP and confirm that the motor is in slow mode. Pulling this plug from the PP did fix the issue, so it's in slow mode.

Since trimming the motor sometimes trips it into slow mode, I'm pretty sure I have a harness problem. I'm debating putting in a new harness or just disconnecting the tan wire at the pack. If I disconnect the tan wire at the pack:

1) Will I still get the temperature and oil alarms?
2) Can I remove just the tan wire from the harness plug without cutting the wire? I read somewhere you could just push the plug prong out, but if you can there must be a trick since mine won't budge.

As always, thanks for your help.
 
They are tricky little connectors. I believe it has a boot on the back side. Pull it out around the wires & away from the connector. You need a small pin or stiff wire to release the tab that is holding the pin in the connector. Push the brown wire in & then try to release the tab. Pull back on the brown wire. May take several times before you find the tab. Can get frustrating!
After you get it it you can test the horn/overheat system by grounding the wire harness brown wire from any sensor. Depending on what year model engine you should get a light or horn with engine off or running. I believe that wire is just to turn on SLOW which occurs in the pack?
 
It is inside the harness, but I have never had to work on one for a sixty degree motor. Parts breakdown shows it, but I don't know if where they show is actual. The older motors had a lump in the harness you could find it that way. Just never looked for it on a newer motor.
 
With respect to testing my diode, should I test the brown wires for connectivity to ground with an ohm meter? Do I test the wires at the sensor or in the plug that attaches to the PP?
 
You are testing with ohm meter from one end of the brown wire to the other end. You will read ohms one way & none the other on the temp sender wires only. Your meter may have a reverse button. (I beieves that is brown/blue stripe). If your leads were long enough you can test all the way to the horn/gauge. Remember the motor has to be running to sound the horn, complete circuit. The gauge drives the horn.
The other brown wires will ohm in either direction.
 
Back
Top