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TOPIC: 1974 merc 85hp idiling issue

1974 merc 85hp idiling issue 14 years 8 months ago #4713

I just aquired a 1974 85 hp merc outboard it runs fine on fast idle,but will not slow idle.can someone please provide some ideas of what could be wrong.

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Re: 1974 merc 85hp idiling issue 14 years 8 months ago #4727

Always start the trouble shooting with a compression test.

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Re: 1974 merc 85hp idiling issue 14 years 8 months ago #4837

As mentioned, check compressions are all good then go through the carbs & fuel pump. Check timing is correct. If all this is good then there are some small plastic restrictors located in the transfer ports on cylinders 1-3. By all accounts these can work free & get ingested, after that the thing will never idle any sense.

I believe I may have the restrictor issue on my '84 115 as it won't idle any sense & everything else is done.

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Re: 1974 merc 85hp idiling issue 14 years 8 months ago #4861

have you cleaned the cap and rotor if it has one.

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Re: 1974 merc 85hp idiling issue 14 years 8 months ago #4870

  • g3jim
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end cap seals?? especially the bottom seals

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Re: 1974 merc 85hp idiling issue 14 years 8 months ago #4884

if lower seal was bad it would pull water in the lower cyl.

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