Inline 6 brittle wires

[ssv1761982]

I just brought home a 1975 150. What is the best way to replace the the brittle wires? Make new pieces and replace them one at a time? What would be a good quality wire to use? I haven't checked this out in detail yet. I wonder how bad the wires are in the wiring harness to the control box.

[Raceman]

I've heard several reasons that the wires in the 70's Merc turn to crap, but whatever the REAL cause, the bottom line is that Merc bought wires from a vendor in the 70's that weren't appropriate for long term in the environment they were placed in, whether it was heat or a fuel vapor rich atmosphere. I've got old 50's and 60's Mercs in my collection that the wires are like new on, but they're rotten in most all of my '74 to '78 stuff.

All that having been said, the only way to do it right is to replace the internal harness and other components with rotten wires. I don't think it's possible to successfully replace 'em on the stator and trigger especially. Rapair has all the stuff you'll need. In most cases the external harness to the control box doesn't rot like the other stuff, so if you DO have issues there you can usually find used ones that still have life in 'em.

I think the '75 model 1500 is one of the best lookin' Mercs of all time. The big blue 1500 on both sides of the top cowl announcing that this was the baddest production outboard available at the time struck utter fear in the OMC crowd back then, and along with the change to the black front faceplate REALLY set it off.

[oldskier]

"In most cases the external harness to the control box doesn't rot like the other stuff, so if you DO have issues there you can usually find used ones that still have life in 'em."

Raceman, I seldom disagree with you but I am working on the control box for my blue stripe Merc 1000 and I just got done trying to salvage the wire harness. The insulation on the wires inside the cable are like dried oatmeal all the way from the control box to the engine plug. I am wiring in a spare from another control box that is somewhat better but the insulation is still brittle. It was the same on the control box on my Powercat. I have a blue stripe 50 hp with a control box on my engine stand right now and it has a control box harness that is the same. That is 4 for 4 on rotten harnesses for me. I have had some success making solder-shrink wrap splices to overcome, but they ain't gonna last forever. I hope somebody starts repopping them soon.

Bernie

[Mark75H]

My 135's insulation was bad on the boat end too. I found heat shrink to cover everything, even the main battery cables.

[Robby321]

Not talking motor here, bad wires. But harness and box. When we were rigging mine, we went through a bunch of harness/control boxes, found what looked like a good harness, right length, and a decent looking box. The harness had some issues at the motor plug. Frayed cables to the batt. Cut in 1/2, did some splicing, and wrapped it up. Then pulled the box apart, for the right size cables. What a mess that key switch was. Whatever insulation was used back then, was real junk. Disintegrated to powder with age. I have no clue of what the main harness, after motor to box would look like though, but seems that the insides it, would survive, and little exposure. Have to find a junk harness, and split it open. Anyway, heres a few pix, what I'm talking about.215444215445215446

[Robby321]

I can't remember what I had to do here at the moment, but maybe think I found, plug end, frayed wire past the motor plug too. I "think"..?..can't remember, I got a good plug, as old was not so hot either. Corroded. We found a decent plug, already had been cut down, but good wires. Heres a pic the splicing. Also another pic, the batt cable splicing in..big electrical wire cable connectors, sold Home Depot, others. Just don't get stupid, like I did, not thinking. Cut them the same place, and when done, said "dumbazz"..they are right next to each other! Good way to fry the brain box. Taped the piss out them, and separated by a good hunk of rubber. always stagger your splices in getting wrapped a harness!..or it looks like a snake, swallowed a pig!. The other pic is the final. Looks like crap, miles of tape..(have a friend works the power company..free electrical tape..what the heck..long as it works, and it does!


215450215451215452

[cvsteve]

When I rewired the Carlson I also replaced the engine and main harness. I then replaced the Mercontrol box as you have pictured and replaced it with the "concealed or panel mount" control box which only shows the shift/throttle handle(used on i/o's mostly). Those controls do not have any wiring to them except the neutral safety switch which can be wired into your harness215456. At that point I decided on a dash mountrd ignition switch with the push to choke feature. It really cleans things up a bit gives you a safer system. If you decide to go that route, I can guide you through it!

[Robby321]

When I rewired the Carlson I also replaced the engine and main harness. I then replaced the Mercontrol box as you have pictured and replaced it with the "concealed or panel mount" control box which only shows the shift/throttle handle(used on i/o's mostly). Those controls do not have any wiring to them except the neutral safety switch which can be wired into your harness215456. At that point I decided on a dash mountrd ignition switch with the push to choke feature. It really cleans things up a bit gives you a safer system. If you decide to go that route, I can guide you through it!

Actually thats the way to go. Get a good plug off the motor, splice in new wire, shrink wrap a new harness, run all the mess of wires the old Merc box, to separate, ING,/choke..neutral start, etc. They got too much stuff, going into that old box. Like my 350 I/O..Morse shift, neutral pull button for throttle, full range the throttle now, rest on the dash. Plus those old Merc boxes, ..well...the right hand throttle "blade"..sux, range too move before stuff happens. No "feel". Best to run a hot foot, right hand for shift only.

[Mark75H]

Steve, do you know where I could find a steering wheel like that?

[cvsteve]

You can check to see if someone over at cgoa.com might have one . I saw one on ebay yesterday t215463hat was a true "wooden" Merc piece. It was was listed as a Mercury steering wheel. I guess I got lucky when I found my Carlson in great condition!215462

[ssv1761982]

Thanks everybody. I only had a couple of small spots that were bare so I used 'Liquid Electrical Tape' for now. I need to splice in new battery cables next. I want to get this running to make sure it is mechanically sound before I spend a lot of money replacing electrical stuff. That is my plan anyhoo, we all know how plans go.

I realize the wires are on borrowed time and will need replaced soon if it runs ok otherwise.

[Robby321]

Thanks everybody. I only had a couple of small spots that were bare so I used 'Liquid Electrical Tape' for now. I need to splice in new battery cables next. I want to get this running to make sure it is mechanically sound before I spend a lot of money replacing electrical stuff. That is my plan anyhoo, we all know how plans go.

I realize the wires are on borrowed time and will need replaced soon if it runs ok otherwise.

Its not a lot of money, just time, doing wires. And again, any little "short out"...could lead to fried electrical stuff, and thats expensive!