Only two cylinders on 100hp evinrude are firing

brown66terry · Oct 19, 2010

I have recently encountered a problem with only 2 cylinders firing.I changed the swith a few weeks ago and took the boat out and then had more problems but the boat seemed to run fine.Took the boat back to the lake and it hardly wanted to start.I finely got it started and it seemed not to be as loud as before.Check to see if all the cylinders was firing and the two right cylinders facing the back of the motor was the only ones working.The night before I tightened the throttle control knob and didn't think about nothing.When I finally got the boat started I moved the switch back and forth and finally the other cylinders fird and smoked like a freight train and then they quit working again.I took the control box apart and didn't see anything that I thought was wrong.Finally after I keep working on it the buzzered went off.What could be wrong that only lets two cylinders fire.

tashasdaddy · Oct 19, 2010

Re: Only two cylinders on 100hp evinrude are firing

year, model # of motor???? which cylinders not firing? if same bank, probably a power pack.

F_R · Oct 19, 2010

Re: Only two cylinders on 100hp evinrude are firing

brown, there are lots of different possibilities. Impossible to diagnose without at least knowing what we are working on.

brown66terry · Oct 20, 2010

Re: Only two cylinders on 100hp evinrude are firing

The engine is a 1979 100 hp evinrude,I can't find the paper that I wrote down the model # on but will post it later.I put a new switch in it about a month ago,the night before I adjusted the the tension on the throttle control,after the engine wouldn't start after awhile,then finally got it started it wasn't as loud and started to see if all cylinders were firing and they wasn't.Started moving the throttle control back off and moving the switch back and forth and finally the engine started firing and smoked like a freight train because of the fuel that got in them and couldn't find the problem after I took the switch out.There is little room for the switch and I thought I might have pinched a wire in the switch.Could I have crossed the two m wires or could the switch even be the problem.

ezeke · Oct 20, 2010

Re: Only two cylinders on 100hp evinrude are firing

Part of your kill circuit is shorted, or you have a faulty powerpack.

Use your ohmmeter to test the circuit between the large red engine plug and the powerpack; the wire will be black with a yellow stripe.

brown66terry · Oct 21, 2010

Re: Only two cylinders on 100hp evinrude are firing

Can you go into more detail on how to do that.I don't know what you mean about Large red plug unless you mean the large red wire.What do i touch the wires to on the oms meter and what should it show.I do beleive I have a short.My ignition has the purple wires also just to let you know.

tashasdaddy · Oct 21, 2010

Re: Only two cylinders on 100hp evinrude are firing

suggest you buy a OEM Service manual, and become familiar with it. wiring in the TOP SECRET FILE.

ezeke · Oct 21, 2010

Re: Only two cylinders on 100hp evinrude are firing

brown66terry said:
Can you go into more detail on how to do that.I don't know what you mean about Large red plug unless you mean the large red wire.What do i touch the wires to on the oms meter and what should it show.I do beleive I have a short.My ignition has the purple wires also just to let you know.

The purple wires on your ignition are for accessory positive voltage and have nothing to do with the kill circuit.

The kill circuit is a grounding circuit which prevents the powerpack from firing, usually activated by turning the ignition key to off.

The large red plug is the connection for the main wiring harness - you will have to take the cover off the engine, then you can't miss it.

http://www.maxrules.com/graphics/omc_pics/REMCONTBOX.jpg

brown66terry · Oct 21, 2010

Re: Only two cylinders on 100hp evinrude are firing

Ok,I get it,I know how to use a meter but I was just asking what wires that I did to touch.I get the black wire with yellow stripe.What does the other end need to touch on the power pack.Do I need to touch the black/yellow wire to the end of the spark plug holder,silver piece and do it with the switch on.I am going to start working on it again tonoight.

:redface:

brown66terry · Oct 21, 2010

Re: Only two cylinders on 100hp evinrude are firing

tashasdaddy said:
suggest you buy a OEM Service manual, and become familiar with it. wiring in the TOP SECRET FILE.

I am familiar with an oms meter.Just got confused on what to do.I was talking about the wires inside the switch box,didn't know he was talking about something on the motor.

F_R · Oct 21, 2010

Re: Only two cylinders on 100hp evinrude are firing

No offense, but you are barking up the wrong tree. The kill circuit will kill the whole motor, not just two cylinders. But if you insist on trying it, just disconnect the black/yellow stripe wire and see if that fixed the problem. You won't be able to turn it off with the wire disconnected. WARNING! If you apply any voltage at all to that kill wire you will damage the power pack.

bktheking · Oct 21, 2010

Re: Only two cylinders on 100hp evinrude are firing

Ok- check the powerpack ground, if not grounded properly you will lose spark to one bank. If that doesn't cure it swapped the packs around, move the good one to the other side of the motor and the suspect in place of the good, if you suddenly get spark on the bank that didn't have spark buy another pack.

emdsapmgr · Oct 22, 2010

Re: Only two cylinders on 100hp evinrude are firing

If you have firing problems on one bank of cylinders, it may be a faulty power pack. You have two packs on that engine, and one controls the spark to each head. Swap the two packs. If the "no fire" situation moves to the other head with the swapping of the packs-you have a bad pack.

Only two cylinders on 100hp evinrude are firing

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