Mercury outboard complete rewire

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Scott
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Mercury outboard complete rewire

Postby Scott » Sun Feb 17, 2013 2:38 pm

Anyone done this? I assume its a hellish task.

This is the first place visited and posted on so bare with me.

I checked out maxrules.com for the wiring diagram thats in color and matches the one in my Merc shop manual. So I got the colors. What are the gauges of wire I need? I also found a marine wire chart on iboats.com

Dare I try? Are there any alternatives?

The motor is a 1975 650 3 cylinder with the switchbox and one coil. All the wiring is toasted, frayed and the casing is falling apart.

Thanks in advanced!
Thun.der.bolt
ˈTHəndərˌbōlt

A flash of lightning with a simultaneous crash of thunder.

An ignition system of early Mercury outboards that not only is a nightmare to diagnose but also improves a marine mechanics competency.

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fergal butler
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Re: Mercury outboard complete rewire

Postby fergal butler » Sun Feb 17, 2013 2:57 pm

You might be able to pick up a second hand or remanufactured harness that would save a bit of work http://www.ebay.com/itm/Vintage-Mercury ... eb&vxp=mtr

Scott
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Re: Mercury outboard complete rewire

Postby Scott » Fri Feb 22, 2013 9:53 am

Mine is about good as that one. See the patina/verdigris starting to appear on the wires? Good point though.

I've found some good info within a little research and by luck stumbling upon some sites.

This one is a really good troubleshooting site for CD/CDI system for outboards and outboard wiring systems:
http://issuu.com/cdielectronics/docs/troubleshootingguide?mode=embed&layout=http%3A%2F%2Fskin.issuu.com%2Fv%2Fcolor%2Flayout.xml&backgroundColor=000000&showFlipBtn=true

And this one is where I found good info on tinned marine copper for engine circuits:
http://www.awcwire.com/ProductSpec.aspx?id=GPTM-Tinned-Copper

I think I'm going to make my own over the winter. Probably make more sense to buy a engine harness... but they aren't tinned and they are made in China and have no warranty.
Thun.der.bolt
ˈTHəndərˌbōlt

A flash of lightning with a simultaneous crash of thunder.

An ignition system of early Mercury outboards that not only is a nightmare to diagnose but also improves a marine mechanics competency.

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steveh41
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Re: Mercury outboard complete rewire

Postby steveh41 » Fri Feb 22, 2013 10:19 am

Try this link:

http://www.marineengine.com/parts/mercu ... /index.php

With your engine serial number you should be able to access the original owner's manual and any available parts.

Also:

http://www.marineengine.com/manuals/sel ... nt=Mercury

The Seloc repair manuals have wiring diagrams which usually specify wire gauges.

pamelalynne1
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Re: Mercury outboard complete rewire

Postby pamelalynne1 » Wed Jun 26, 2013 6:50 pm

The toasted harness scenario is quite common.
I checked all my suppliers, including Marine Engine.com, Pro Marine and CDI Electronics and have not found a wiring harness available for the 1975 650. No part number is listed for it at all.
The Clymer manual B726 covers your motor and has the wiring diagram for 1975 on page 354. If you plan to do any work on the motor the manual is a good investment.
It is time consuming; but if you are determined and patient you should be able to make your own harness, that is if the connection blocks are in good shape. If you need to replace it the switch box is available from Pro Marine. Part number 114-4796 The list price is $392.00 with a dealer cost of $196.00 You should test the switch box and the trigger according to CDI's instructions before you decide to go any farther.

The website for the CDI troubleshooting guide is: http://www.cdielectronics.com/support/
Hope this helps.

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TUGMYWAY
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Re: Mercury outboard complete rewire

Postby TUGMYWAY » Wed Jun 26, 2013 8:25 pm

The motor plug to control harness you will not find. So do a hard wire to all the parts. The plug-in harness was for faster rigging when new.Only problem I can think of is the stator wires ( yellow/red ) maybe a pain to tap into with new. :shock: And the trigger wires (same thing ) :shock: Try to find some fine ,high count wire for the trigger (its light maybe 16/18 ga. ) this will let if flex when the trigger moves. The trick will be the splice. Look for insolation that is still in ok shape. (Good luck with that) :roll:

The next problem will be the control box wires! They are in the same shape or,will you know. If it still works? DON'T open it up!!!!!!!!!!!!! :shock:

Some time if all the wires still work I tell owners to get some clear spray paint and paint the wires! Some will be green with oxidation . This is a good thing. But do not try to tape it up. That is BAD! Just spray it with the clear paint. This will help keep out water.

Also give it a new water pump!!!!!! The 3 cyl's will "DIE" fast with a poor pump!!!

Just my 2'c's. :D

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galamb
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Re: Mercury outboard complete rewire

Postby galamb » Sat Oct 05, 2013 8:43 am

If the motor will be run in fresh water then you can use (regular) automotive wiring if you opt for the "do it yourself" approach.

Obviously you will not be able to get the wire colours correct (never saw green/white stripe at discount auto places), but if you get a selection of colours and keep good notes (for future reference) you can rewire it inexpensively.

Alternately, many marine suppliers can get you the exact colour codes, but usually at triple the price of standard wire.

Tinned wire (my opinion) is un-necessary in fresh water and only slightly better than regular in a salt environment (salt is going to eat the wire unless you keep it well "fogged" with fogging oil - should be done annually at least in fresh water environment as well).

Until you get "past" the coils (so spark plug leads) there is no voltage in Merc T4 ignition that exceeds 360 volts/20 amps (and most often 9 amps max). If you look at the wires you are replacing I think you will find the majority would be in the 14 or 16 gauge range(or smaller and somewhat less than 2 feet long).

If you need some additional help you can pop over to http://www.marineengine.com (noted here as a source for manuals etc) and click on the very bottom left corner of their main webpage. You will find the "boat repair forum". Follow that link and post up in the Mercury outboard section. I advise quite a bit in that section and know a couple of guys there quite well that can walk you through the process..
Graham

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