Weird electrical issue with a 1971 50hp 50173s Evinrude

J

Jeffthefisher

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Apr 15, 2012

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4

• Apr 17, 2012

• #1

My 50 hp Evinrude is not firing unless I remove the top plug. With the top plug removed it starts immediately on the 2nd cyl. At this point in the process I have spark at cyl 1 wire and plug. If I screw in the #1 plug I lose all spark to both cyl. Here is the kicker. I lose the spark even when I don't have the wire connected to the #1 plug. This has stumped one seasoned marine mechanic and it just doesn't make any sense. Any help would be appreciated. Thanks ahead of time.

 

D

Daviet

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8,958

• Apr 17, 2012

• #2

Re: Weird electrical issue with a 1971 50hp 50173s Evinrude

Do I read this correctly, you have good spark with both plugs out, you screw in the top plug and loose spark to both cylinders?

 

J

Jeffthefisher

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• Apr 17, 2012

• #3

Re: Weird electrical issue with a 1971 50hp 50173s Evinrude

Daviet said:

Do I read this correctly, you have good spark with both plugs out, you screw in the top plug and loose spark to both cylinders?

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That is correct. The top plug isn't even hooked up to the plug wire. It starts instantly with just the bottom plug in and hooked up. I am really baffled! It just doesn't make sense at all.

 

B

boobie

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• Apr 17, 2012

• #4

Re: Weird electrical issue with a 1971 50hp 50173s Evinrude

With both plugs in, is this mtr spinning over good and fast or just grunting ?? You need approx 250-300 rpm for this ignition system to work.

 

J

Jeffthefisher

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• Apr 17, 2012

• #5

Re: Weird electrical issue with a 1971 50hp 50173s Evinrude

boobie said:

With both plugs in, is this mtr spinning over good and fast or just grunting ?? You need approx 250-300 rpm for this ignition system to work.

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It seems to spin really good and isn't grunting at all

 

G

glenn property of pam

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Feb 17, 2012

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• Apr 17, 2012

• #6

Re: Weird electrical issue with a 1971 50hp 50173s Evinrude

only thing i can think of that the top plug (lead disconnected) could mess with the ignition is if there movement in the top bearing or the starter like boobie said isnt able to reach min speed.

 

J

Jeffthefisher

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• Apr 17, 2012

• #7

Re: Weird electrical issue with a 1971 50hp 50173s Evinrude

glenn property of pam said:

only thing i can think of that the top plug (lead disconnected) could mess with the ignition is if there movement in the top bearing or the starter like boobie said isnt able to reach min speed.

Click to expand...

Thanks for that idea. That has some real plausibility. I will do some more work with that idea hopefully later this week. Thanks loads. I will try to let you all know how it turns out.

 

Scott Chinsota

Petty Officer 1st Class

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Apr 18, 2011

Messages

216

• Apr 20, 2012

• #8

Re: Weird electrical issue with a 1971 50hp 50173s Evinrude

can't help with this particular issue however i also run a 50173s.

 

Bosunsmate

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Apr 7, 2012

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6,129

• Apr 20, 2012

• #9

Re: Weird electrical issue with a 1971 50hp 50173s Evinrude

If you could post compression readings that would be good

 

Scott Chinsota

Petty Officer 1st Class

Joined

Apr 18, 2011

Messages

216

• May 14, 2012

• #10

Re: Weird electrical issue with a 1971 50hp 50173s Evinrude

just a suggestion...try testing at night. if the coil wires are leaking voltage, current could arc to the tip if the exposed plug or to the block. if arcing occurs, you'll see a light show!