Mercury 800 Wiring Damage

Electrical and electronic topics for small boats
Peter3
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Joined: Mon Oct 03, 2022 10:28 am

Mercury 800 Wiring Damage

Postby Peter3 » Mon Oct 03, 2022 5:47 pm

On a Mercury outboard engine model 800 there is obvious heat damage to several of the wires.

Q1: Is heat damage to the wiring on a Mercury 800 outboard common?

jimh
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Location: Michigan, Lower Peninsula
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Re: Mercury 800 Wiring Damage

Postby jimh » Mon Oct 03, 2022 5:51 pm

On older outboard engines, say ones from the 1970's, which are now approaching or are over 50-years old, the electrical wiring on the engine itself can often become damaged from old age and exposure to heat. Use of rubber wire insulation was common in outboard engines of that era, and now, in 2022, 50-years of drying out can cause the rubber insulation to crack and break away from the electrical conductor.

I am not aware of any statistical data about the frequency of occurrence of 50-year-old electrical wire insulation becoming dry and brittle, but I do not think it is particularly unusual.

Peter3
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Joined: Mon Oct 03, 2022 10:28 am

Re: Mercury 800 Wiring Damage

Postby Peter3 » Wed Oct 05, 2022 7:41 pm

I stripped back the wire for the stator wire as far as I could. [The conductor is made of aluminum or magnesium, and] hence the corrosion. To replace the stator and the trigger coils seems straightforward. As long as I have access to the coil assembly I may as well replace both stator and trigger coils.

With the engine running I tried to read the voltage at the battery; I did not see any increase. I may need to keep an eye on the battery charge this season.

I was finally able to get the Mercury 800 engine to run at a low idle speed. This was a big win for me.

The gasoline fuel in the tank must have been old. The engine has been laid up for winter so there will be no more updates to follow.

jimh
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Re: Mercury 800 Wiring Damage

Postby jimh » Thu Oct 06, 2022 7:50 am

Marine wire would never be aluminum conductors. The wire should be tinned copper wire. An aluminum wire would be completely inappropriate for use in any marine electrical circuit. If the wire really were aluminum, perhaps that is the cause of so many problems with these older Mercury electrical systems.