1979 85hp evinrude will only fire on 2 cylinders

i have a 1979 85hp evinrude motor that is only fireing on the bottom 2 cylinders
i need to know how to fix the problem.

Re: 1979 85hp evinrude will only fire on 2 cylenders

Re: 1979 85hp evinrude will only fire on 2 cylenders

Make it fire on 4 cylinders, that's how you fix it.

How do you know it's only firing on 2 cylinders, did you do any testing to come to this conclusion or are you guessing, or did someone else tell you this?

If you did testing then you would know if it's a spark or fuel issue, my guess is it's a fuel problem rather than spark being it's the bottom 2 cylinders, put some premix fuel in a spray bottle and spray it in the carb while the motor is running and see if those bottom cylinders pick up.

Re: 1979 85hp evinrude will only fire on 2 cylenders

Re: 1979 85hp evinrude will only fire on 2 cylenders

Sixmark said:

Make it fire on 4 cylinders, that's how you fix it.

How do you know it's only firing on 2 cylinders, did you do any testing to come to this conclusion or are you guessing, or did someone else tell you this?

If you did testing then you would know if it's a spark or fuel issue, my guess is it's a fuel problem rather than spark being it's the bottom 2 cylinders, put some premix fuel in a spray bottle and spray it in the carb while the motor is running and see if those bottom cylinders pick up.

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i have already took the hole fuel system apart and checked it. the problem that i have
is that the boat will only open up half way. i checked the fireing bye pulling all the spark plugs out and haveing my wife turn the key over while i held the plug and grounded it to a bolt on the head while the motor was being turned over to see if it was fireing. the bottom 2 had good fire and the top 2 did not have any. these are brand new champion plugs.

Re: 1979 85hp evinrude will only fire on 2 cylenders

Re: 1979 85hp evinrude will only fire on 2 cylenders

I like to use an inductive timing light on each plugwire while running the engine. The flashes from the gun will indicate no fires, weak firing, or intermittent firing. You can switch the coils from top to bottom, then re-test. If the results are the same you know it is not the coils. That engine has two interchangeable power packs-one for each head. Since the problem is on both lower cyls, both power packs could be the problem. The other two expensive components are the stator and the timer base, either of which could contribute to the problem. If you don't have a factory service manual, you may find the online troubleshooting/test information from CDI Electronics to be helpful. You will need a special "peak reading" voltmeter to perform some tests.