left bank fireing twice as often as right

R

river runner

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Oct 3, 2006
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Can anyone tell me why #2&4 cylinders fire twiceas often as #1&3. I found this with a induction tach when 1&3 are reading 1000 rpm 2&4 are reading around 2000.this seems to be causing a missfire and a lack of power.
 
D

DHPMARINE

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Dec 16, 2003
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3,688
Re: left bank fireing twice as often as right

And the lucky motor is a ........

Could be anything depending on what you have,but are you sure you don't have 'over-flash' because you are reading this inductively ?

A spark tester set at 7/16 " will help you further test the ignition system.

DHP
 
Joe Reeves

Joe Reeves

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Feb 24, 2002
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Re: left bank fireing twice as often as right

I assume that you have a engine with dual powerpacks.

If indeed the port bank is double firing, the cause would be a faulty diode in the opposite (starboard) powerpack. The cure would be to replace that starboard powerpack.

You can test the diode with an ohm meter, connecting between the black/yellow wire and the white wire. You would obtain a reading in one direction only on a good diode, but a reading in both directions on a faulty diode.
 
R

river runner

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Re: left bank fireing twice as often as right

Sorry the motor is a 1990 140hp Evinrude it checks fine on the spark tester at cranking rpm it even sounds great for the first 20 seconds or so after it starts, then the rpms drop and it starts to miss.
Capain Joe this motor only has a single power pac
 
Joe Reeves

Joe Reeves

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Re: left bank fireing twice as often as right

That engine has the "Fast Start" feature whereas the spark is electronically advanced when first started until it reaches a certain temperture.

At that set temperture, that advanced spark ceases, dropping the timing back to its normal idle rpm. With this in mind, is it possible that you simply have the idle set too low?

That engine, when warm and running on a flushette in neutral, should idle at approximately 1400 rpm.
 
R

river runner

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Re: left bank fireing twice as often as right

I had the boat in the water when I was testing it don't know what it runs at on the water muffs. I just received a DVA adapter I ordered, I'm going to give the ignition systemthe once over. I'll let you Know how I make out.
 
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