OMC remote controls with the big red plug…

[johnyrude200]

well I think I figured out what the issue was. I ran through the process step by step of tracing continuity through the ground circuit, and what the problem was, is that the control box side of the wiring harnass has a different configuration of connectors.

So the black and black/yellow leads on the motor side, which the key should provide continuity for (closed circuit) when in the OFF position, doesn’t have a connector in one of the holes which the motor-side plug connects too. Therefore, no way to close that circuit in the OFF position and ground out the ignition system, killing off the motor.

I didn’t realize there is even much of a difference between these control boxes in the first place.

The box I am using is off of a newer motor (probably mid 80’s). After looking at either harness (either motor or control box end), it appears that the motor end is much simpler than the control box. These plugs appear to be molded and not modifiable, unless you drill out one of the holes to put the pin in where it needs to be.

Looking even further between some wiring schematics from a ’79 service manual, and an ’88 service booklet, these harnesses are totally different in terms of plug configuration. I’ve seen some motors pass through here where previous mechanics just spliced butt connectors and reconfigured things, abandoning the original big red/black plugs. Looks like I may have to do that to retrofit this control box to this older motor.

[fleetwin]

Do the big plug colors match? Black harness connectors are NOT compatible with red harness connectors. The earlier 25/35hp harness connectors were black, they must be mated to the black connectors/wiring harnesses meant for these engines.

[johnyrude200]

Ah, yes. The motor has a black connector, the control box has the red one. I was going to just use butt connectors to make the correct wires matchup with each other. There is still a white and grey wire on the control box side, but I’d just make sure they weren’t connected to anything. I believe I have a dead, newer style 25hp (80’s), which I can cut the motor-side plug off (red), and splice onto from the older style 35hp I am working on. Any words of wisdom/warning with this?

Earlier in the year I saw another mechanics handywork retrofitting a 1985 25hp motor with a new style BRP control box (2000’s). I’m guessing that as long as the correct wires are lined up, things should still work OK? The motor worked fine using that control box.

[fleetwin]

PS- Sorry I didn’t explain this earlier. Your post says: control box wiring with big red plug
One of your later posts explained you were working on a 1978 engine, these use black connectors. I should have remembered this when I read your posts. There were no remote control box with integral key switch made for these engines, the two lever control boxes were mated with a special wiring harness with a black plug connector designed for these engines. I don’t think the red plug connectors were used on these engines until 1980.
Don

[johnyrude200]

Oh OK, well at any rate, to pick your brain – I should be OK making up my own plug for the motor using a newer motor-side red plug and splicing onto the existing wiring for this 1978 motor?

I just walked out to my garage and do have a used red plug connector off of a donor motor with wiring intact, so it would just be a matter of snipping the black plug off, splicing onto the engine wiring harness, and using the plugs as is.

[fleetwin]

I’m don’t think I understand what you are describing. I am assuming you have an engine with a black plug connector and you are trying to mate it up to a remote control with a red plug connector, correct?
Do you have a donor motor with a red plug engine harness? If so, that would be ideal, no need to snip the plugs off, simply use the donor red plug engine harness on your running engine that currently has the black plug.
Snipping the plug connectors off should only be done as a last resort. Splicing these harnesses togehter means the engine can’t be removed from the boat without removing the engine harness. Spliced connections are always troublesome, especially the black/yellow connection in salt water.
Again, your description is a little confusing, so am not sure I understand what you are proposing to do.

[johnyrude200]

Yes, I’m trying to update my ’78, black-plug motor to accept a newer red-plug harness, so I can utilize more modern control boxes. I don’t know where to get my hands on a black plug wiring harness, and I rather just use a newer style control box.

I have an old red plug (engine side) but not the complete harnass, so I can’t just swap out the wiring harnesses. What I am planning on doing is snipping the old style black connector off the motor (I’ll leave a little bit if someone decides to restore it some day), and essentially updating it to accept any red-plug control box. It will allow for the motor to be unplugged at the usual spot if necessary down the road (this is going to be my personal motor anyway).

My question is, this job is as simple as splicing the newer style red plug harness and making sure the correct color-coded wires are mating with the newer style red-plug control boxes, correct? I’ll obviously makes sure where I splice on a new red-plug harness plug, that those are clean and encapsulated splices for longevity.

[johnyrude200]

Moving further along in this process…

Basically the older style black plugs have 5 leads.

black for kill switch
black/yellow for kill switch
purple/white for electric choke
yellow/red for key/starter
red/purple for key/starter

The newer plugs have 3 more leads.

purple for accessory/alarm
grey for accessory
tan for accessory/alarm

After a good conversation with T2Stroke, considerations have to made for the neutral lockout switch too, and in this case, we have a situation where there is one on the motor, and a 2nd one in the updated style control box. If either read forward/reverse gearshift, it stops electricity from flowing through to the starter by creating an open chain circuit.

In my case, I am going to try leaving both on the motor and control box because this motor is also a tiller control with manual starter. So if I ever end up using the motor as a tiller motor, then I still want the neutral lockout feature (or if I sell it off some day, safety for the next owner).

I’m not sure how leaving both neutral lockout features can cause any problems, since the yellow/red wires essentially are creating a river of electricity, and those lockout switches are simple ‘breaks’ to stop the flow of power if either is open. Both switches just allow the electricity to be grounded and flow; power goes in, then is grounded to the motor. If the switch is open, then that electricity doesn’t keep flowing.

I mean, let’s say my control box fails somehow, or a cable breaks, or whatever, and I end up having to steer home using the tiller and removing the shift/throttle cables. I’ll have to either leave the key in the ‘on’ position, or just unplug the harness to use the motor as a tiller/manual start motor.

Not as complicated as I thought. I will say that looking at electrical schematics of the motor plug from ’78, and the control boxes from the 80’s, the diagrams are inaccurate (they forgot to reverse the color scheme for plug/wiring layout for the plugs). I ended up tearing apart the control box and using the continuity tester to verify which plug leads where what in the plug end. They were opposite of the service manual diagram, and the diagram ISN’T a mirror image of what you’re looking at.

[fleetwin]

OK, I think I understand now, you just have an engine side red plug that someone has cut most of the harness off, correct? In other words, you only have a few inches of wire harness bundle coming off the red plug.
Yes, you could certainly do a neat job of extending what is left of the harness leads using shrink tube/solder/crimp to make nice water tight connections. No need to extend the unused purple/tan/grey leads, just seal off the wire ends. Don’t chop up the original engine harness to use the leads, save it "just in case" like you mentioned. I think the wiring is 14gage, so you can just buy a few feet of red/black/yellow(for solenoid B+)/purple. I realize some of the same colored leads would be used twice, but you could always look back at the wiring before the splice to differentiate between the like colored leads.
Finally, there is no harm/problem in leaving both start safety switches in place. BUT, I think the control box safety switch makes/breaks the positive input to the solenoid, while the engine mounted safety switch makes/breaks the negative input to the solenoid. So, you would have a safety switch/circuit on both positive and negative inputs to the solenoid. In other words, don’t put both switches on the same lead, or you will have a direct short.
Finally, you will want to put a 20 amp fuse between the hot side of the solenoid (battery lead post) and the red/purple lead in the harness for safety.

[johnyrude200]

I ended up taking the motor side neutral switch (yellow/red wire) and just disconnecting that off the solenoid, then wiring up the control box as normal, everything works fine. I can always reconnect if necessary in the future.

Looking more closely at the black vs red plugs on the motor side, the biggest difference is the configuration for the stop circuit. That got moved, pretty much the rest of the stuff (starter, choke, on position) are the same, but the accessory stuff is reconfigured.

It gets even more interesting if you go back a couple of years to ’76 (which, coincidentally, a customer brought one in for me to look at). I wouldn’t even bother trying to update that motor, given all the things going on with that 1st year version.

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