Need help with 2 cylinders not firing all the time.

I have a 1979 Evinrude 115hp and I had a problem with 2 cylinders not firing at all. It turns out that the guy I bought it from had rigged up the power pack and reversed the wires. Now I have changed the wires and the cylinders only fire sometimes. I took the boat out yesterday and noticed that I would get all four cylinders in the begining at full throttle but when I would cut back on the throttle I would lose the 2 cylinders and when I tried to go back to full throttle I would only have 2 cylinders and they were running rough. After that I would get little burst of all four cylinders but most of the day I was only running 2 cylinders. I tried squeezing the priming blub at full throttle and that didn't help. Any ideas?

Thanks,

Matt

Re: Need help with 2 cylinders not firing all the time.

There is some testing here. Just scroll to your year/hp

"http://www.boatpartstore.com/page28.asp"

How do you know you are losing 2 cylinders? Which 2 exactly?

Re: Need help with 2 cylinders not firing all the time.

If priming the bulb actually made a difference, you have a fuel delivery problem. I would still start with a spark, compression test. Don't run the engine as is, your certainly not doing it any good, especially if the carbs' are not feeding fuel-oil mix to the engine.

Re: Need help with 2 cylinders not firing all the time.

I have good compression and priming the bulb didn't help. I have done the spark test and it was fine. The 2 cylinders that aren't firing are on the left hand side if you were looking from the back of the boat. The way I know I'm losing 2 cylinders is the performance. When all cylinders are firing i can go about 40 mph but when the 2 cut out i only go 15 mph.

Re: Need help with 2 cylinders not firing all the time.

Since the same side (port or starboard) is the issue, I would start by testing the Power Pack as per the link posted. If it were fuel delivery, it would affect side by side cylinders, and not be partial to one bank.

Re: Need help with 2 cylinders not firing all the time.

I am having trouble finding the wires that this testing procedure are talking about. "Check the timer bases resistance from the white wire to the blue, green, pink and purple wires. Reading should be 38-42 ohms." Can anyone tell me where to look? I am not sure where the timer base is located.

Re: Need help with 2 cylinders not firing all the time.

It takes a peak reading volt meter to do this properly, but a running test would check voltage from sensor to pack, pack to coils. Have you checked coil output? They should fire across a 5/16-3/8 gap with the plugs in. It is doubtful that both coils would fail at the same time. I should mention, a peak reading meter will also check cranking voltage. Without the meter it would be just a guess, sensor, or pack.

Re: Need help with 2 cylinders not firing all the time.

Lets try to make this easy without a DVA meter.

I would first look to the Power Pack as stated before, it is possible, yet rare, that both coils would fail at the exact same time.

Swap the known good pack with the suspect one, the one on the port side, and see if the problem follows. If it does, the pack will need to get changed.

If the problem does not follow, try swapping the coils with the known good ones and see if the problem follows them, if it does, replace the coils.

The best way to observe spark is with a timing gun, although an inline spark tester with the gap set to 7/16 of an inch will work. IF these tests fail, we will have to move on to the sensors, which you will need a meter.

Re: Need help with 2 cylinders not firing all the time.

The timer base is located under the flywheel on the motor. The timer base has sensors embedded in it, which tell the powerpack(s) when to release a charge to a given ignition coil.

The problem that you are describing is a common symptom of one or more bad sensors. To do a static test of the sensor coils (engine not running) you do an ohms check of the sensors by putting the meter between each of the sensor wires and the common wire, one at a time. Your manual will tell you what value to look for. As an example, on my Johnson ('72 65hp) the correct value is 8.5 ohms, plus or minus 1 ohm. I don't know the correct value for your motor but it is likely to be at or near a single digit value, so be sure to have your multimeter setting on a low range. It is also important to make sure you "zero" the meter before doing the test - look for a small thumb wheel on the meter.

Just out of curiosity, are you sure that the previous owner had sensor wires on the wrong terminals? I would think that the motor would exhibit major problems if this were so because cylinders would be firing at the wrong time. Regardless of this, however, make sure you reconnect the wires exactly as described in the maintenance manual.

Re: Need help with 2 cylinders not firing all the time.

I just tested the stator, sensor coils, and charge coils. I only did the resistance test. They came out good.

One thing I forgot to mention is that when I plugged in the back navigation light, the motor made a loud popping sound and even made the motor twitch. Ever since that the tach has not worked. The tach gives a reading of 5500 rpm (this is after the popping sound, it used to work) when you would turn the key a little bit (accessory position i guess), but now it doesn't even work. The replaced the rectifier and that didn't fix the problem. The previous owner had the back navigation light wired to the starter solenoid, which I suspect is the problem. What else could cause the tach not to work. Could this be related to the problem of 2 cylinders not firing?

Re: Need help with 2 cylinders not firing all the time.

I would expect a long string of posts on this one. I will start with," I don't have a clue"

Re: Need help with 2 cylinders not firing all the time.

Wow! This is a scary sounding previous owner!

Re: Need help with 2 cylinders not firing all the time.

WOW. Let's eliminate problems.

If you do not have a manual, get one, it will be worth the money 100 times over.

disconnect all wiring from the engine except what is required to run the engine, IE factory wiring, disconnect all wires to the boat from your battery, this way can trouble shoot the engine and not have other factors figured in.

when doing electrical work always try to use resistance measurements instead of voltage checks. resistance has no possibility of tearing up or damaging components.

the loud POP you heard was most likely your rectifier BLOWING up from a cross wired light or corroded connection causing reverse bias on your bridge rectifier.

Re: Need help with 2 cylinders not firing all the time.

Sometime today or tomorrow I will do that and let you know when I do. thanks

Re: Need help with 2 cylinders not firing all the time.

It is easiest to check for 12-volt power and proper ground first. A volt-ohmmeter or 12-volt test light are great tools for this procedure. Simply ground the meter or light, turn the key on and touch the positive probe to the purple wire on the back of the tach. You should see 12 volts indicated on the meter, or if you?re using a test light, its bulb should illuminate. Reverse the leads to check for proper ground, or use the ground wire on the tach to ground your meter or test light.

If either the power circuit or ground is the culprit, you can repair the problem and the tach should work fine. In a no-power situation, see if your tach has an inline fuse. These often blow due to constant vibration, or the loud pop you heard . After inspecting for power and ground, if it still doesn?t work, it?s time to check the signal-input source, or the tach itself.

A simple way to determine if the tach is bad is to use another tach. Some shops will have a tach ready with alligator clips just for this, ask them and see if they will let you borrow it, or borrow one off a buddy.

In the event you don?t have access to a shop tach, you?ll have to refer to the manual to check the signal source. The signal is a pulse-positive output that?s provided directly from the stator assembly through the rectifier. A peak-reading voltmeter set to ?positive? and the lowest volt scale will enable you to read any voltage output (on this circuit) from the stator.

Check the procedure and specifications for your engine, since the inspection point, procedure and wiring are not the same for all outboards. In addition, your ohmmeter can be used to check the continuity of the stator windings, as well as the integrity of the rectifier diodes.

If everything still checks out, you will need to test your rectifier/regulator as per your manual. I realize you already replaced it, but may have blown it again unfortunately.

http://ww2.tflx.com/pdf/obtach~1.pdf

http://ww2.tflx.com/PDF/99320.pdf

Re: Need help with 2 cylinders not firing all the time.

I disconnected all unnecessary from the motor. Then I ran the motor and shot a video of it so you could see what I am seeing. I thought maybe it would help you diagonse the problem. I will test the tach signal and power and ground. Thanks for all the help.

I also have a video of the motor running from October 31 2007. You can tell after watching both videos that in october only 2 cylinders were running then the one I took Feburary 29 2008 shows all four cylinders running for a few seconds.

Here is the link for the video in October

"http://www.youtube.com/watch?v=Kr8UolMZwIk"

Here is the link to the video I shot today

"http://www.youtube.com/watch?v=B2tDDuxUdts"

Re: Need help with 2 cylinders not firing all the time.

Did I miss the part about what happened when you swapped the power packs?

BTW, if you even think that your rectifier is bad, disconnect it. You don't want it connected while you do your tests, but it can destroy your ignition system, and that is a real concern.

Re: Need help with 2 cylinders not firing all the time.

I cannot swap the power packs because one of them doesn't have the original harness. The side that I suspect to be bad is the side that had its power pack wires cut and then put back together with electrical tape and connectors. I could swap the power packs but that would require me to cut the connector off of the good one.

Re: Need help with 2 cylinders not firing all the time.

Well, it sounds like you may want to replace the jerry-rigged power pack for piece of mind anyway.

Do ya? If so just go ahead and see if that solves the problem.

Re: Need help with 2 cylinders not firing all the time.

I tested the voltage on the tach between ingition and ground and got 12.6V. When I turn the key to ignition position the needle doesn't move at all, when before it would jump up a little bit. Does that mean the tach is bad?