1989 88 spl Evinrude

ljf

Seaman
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Mar 3, 2006
Messages
51
I recently discovered that my outboard had been running on 3 cylinders and when I replaced the connector going to the input of the coil, a big increase in rpm and power. What surprised me is the engine idled fairly smoothly while the
4th plug was not firing. Can anyone tell me how this was possible? I thought the ultra clean plug in that cylinder was a little strange.
 

SparkieBoat

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Aug 17, 2009
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3,643
Re: 1989 88 spl Evinrude

you would be suprised at how many 4 cyl motors are runnning on 3
 

bktheking

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Jul 29, 2008
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Re: 1989 88 spl Evinrude

They will idle smoothly with 2 on one bank not firing as well. If you look at how an engine works it is balanced using counterweights build into the crankshaft. Those counterweights will still move the same just not as fast as you stated if 3 out of the 4 are working, the motor isn't physically damaged, it just isn't firing on all 4.That's why you see the difference at high rpm, cause at idle the motor isn't working at all and it doesn't need all 4 plugs firing to operate any different. I've got a ninja 1000 sitting in my garage that will idle like a dream if I pull the number 3 plug out, it's pretty cool stuff, put it back in and hook it to a plug wire and it will knock like a SOB, it's got a bad piston pin.
 

bktheking

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5,057
Re: 1989 88 spl Evinrude

Oh ya and depending on how longs it been like that you may want to run seafoam through it just to clean up the motor.
 

ljf

Seaman
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Mar 3, 2006
Messages
51
Re: 1989 88 spl Evinrude

Thanks for the replies. I'll pay more attention in the future.
 
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