OMC Cobra 2.3l running issues

[runarb]

I did a voltage test with ignition switched on and motor not running. Now it has electronic ignition so there are no points to connect as the Stern Drive Manual describes in their test, but voltage dropped from 12.5 to 12.2V at the hot side of fuse box when switching on so I'm assuming the electronic ignition is functioning as points connected. I got the following readings:
A) Battery between + and - 12.50V
B) Fuse box inlet 12.20V
c) Hot side of ignition switch 12.07V
D) Output from ignition switch 12.00V (I have the man over board switch bypassed therefore not listed)
E) Input to resistor wire 11.57V

The stern drive manual says if difference between A) and D) is less than 0.8V then everything is okay. And this number is 0.43V in my case so I think ignition switch loop should be okay. (when points are closed, I don't have points any more but think electronic ignition is connecting).

Does anyone see anything wrong with those numbers? Stern drive manual also says drop in each connection can be 0.2V. From battery to the fuse box this is 0.3V, but there may be several connections, I'm not sure. I should probably locate them and see if I can reduce this first drop.

Then between D and E there is 0.43V drop. Is it normal or should I look for something there?

[Nauti_Mike]

For a non-running engine the voltages look good to me.

[runarb]

I think I have found my problem (if I didn't create a new one). I opened the wire harness plug (see picture) to see if all the pins were looking good and to put some dielectric grease on them. After closing it and after putting power on I heard some clicks from the ignition parts if I moved the plug. Also voltage dropped and came back at the coil depending on how I twisted it. It seems it's rather related to the wires into the plug rather than the pins inside. I guess some of the wires there are almost broken apart. I see it's not possible to open this plug and reconnect wires. Any suggestion on what I can buy to repair this connection? Easiest would be to work with installing a new plug rather than rewiring the whole engine. I appreciate any suggestion.

[Nauti_Mike]

I’ll defer to one of the OMC guys on the site. The Mercruiser 10 pin engine harness is know for corrosion on the contact side of the pins and sockets. Sounds like you are says the wire connections to the pins or sockets are intermittent. I’m not sure a replacement connector is available.

[PickleRick]

We deal with obsolete wiring harnesses quite often in the outdoor power equipment world. When only the connection at joint plug is bad we replace it with something like this.

https://www.google.com/aclk?sa=L&ai=...ECAEQSw&adurl=

Obviously this one isn't likely the one you need. In the case of a plug with different size wires, say one 10 gauge wire and six 14 gauge wires we will use two plugs instead of one and so on.

We don't rewire an entire engine or piece of equipment over one plug with some pin corrosion issues. We only rewire from scratch if there's major corrosion or badly shorted wiring all over the harness.

[runarb]

Excellent thanks. This should work if I decide to go this route. I will open it again and try to locate the wire giving me issue. If it’s a single wire or a couple then I could even run them separately.

[PickleRick]

You're welcome.

Running them individually with bullet or spade connectors is fine but those are usually not water proof. But it will definitely get you back on the water! A little electric grease and heat shrink goes a long way in protecting connections over time.

[Metrodriver]

I sprayed corrosion-X in my plug to clean up the contacts.
I fly old large aircraft and quite often we have wires broken at pins inside connectors. Some are ok to deal with but when one pin renders the one toilet inop on a 13 hour flight with 8 people.... You'll want to give the mechanic who finds it a Nobel Prize...

[runarb]

I disconnected the plug again and 4 of the pins came out with the female connectors on them and wires broken and it’s obvious the wires were corroded at the female connectors. I bought an used engine wire harness on EBay. Not my first choice, but it looked good on picture and was only 25 dollars with shipping, it’s on its way. Didn’t see this part being sold as new anywhere. It’s only 10 or 11 connections at the engine and looks doable. Chances are it’s as corroded as mine but I might get lucky. If not then plan B is to install a new plug. This may need to wait a little as I’m getting busy with other things. I appreciate everyone’s help. I think I’m on the right path.

[builderdude]

You may be able to use a Mercruiser replacement or as pickle Rick suggested make your own.

[runarb]

I'm actually leaning on cutting the plug out and reconnecting. I'm kind of leaning towards using connection boxes as shown on picture. That way I can allways reach each individual connection in the future and check them out if anything goes wrong. I will need 2 boxes for my 10 or 11 wires.

[PickleRick]

It's almost July. If you're not in Florida your boating season is nearly over!

[runarb]

I decided to cut the plug and connect the wires. Everything went well. The boat is running on mufflers as we speak, and has been for 45 minutes. I used the time to adjust the ignition timing and idle speed. I’m not 100% happy about the idle. I could run it on 1000 rpm anything lower will probably make it stall. I decided to let it run 1200 as idle. I measured voltage on alternator. Sense and voltage to coil fluctuates between 14.49 to 14.72 say every 20 seconds. The voltage to the electrical choke is only 7.5v both on alternator outlet side and on choke side, not enough to open it so I tied it open.

what do you think regarding the fluctuations in voltage? Is this normal? At least the 7.5v to the choke can’t be right so something must be wrong with alternator, maybe just best to replace it?

At least it’s a good sign boat seems to run on mufflers without stalling now.

[dktool]

Without it idling @600 to 700 rpm your going to have miserable and potentially damaging shifting.

[builderdude]

Agreed👍🏼

[Nauti_Mike]

Idle rpm is way to high. This will make it hard to shift and put extra strain on the clutch. Are certain the voltage isn’t changing because the rpms are changing?