130 HP Johnson - 1995 - Bad Misfire - Need Help

[Striper500]

I recently purchased a boat with a troublesome motor. The engine and boat are a 1995 which were purchased in 1998 and not used too much. The engine has good compression on all four cylinders from 125-130. The motor starts easily, and once running it will have a loud popping sound that occurs once every 20 seconds or so. The engine has good plugs and plug wires. I spoke to the local OMC mechanic who told me that it could be the ear muffs and that the boat should really be tested in the water to create back pressure. Unfortunately the river was frozen today, but I did manage to submerge the lower unit in a 55 gallon drum - this did not help at all. Once the motor warms up it's least noticible at idle. But when the motor is revving at 2-3000 RPM's the boat shakes when it misfires. Any ideas here ? Anyone seen these symptoms before ? Where would you begin ? Carbs ? Coils ? Timing ?

 

[Dhadley]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

First of all you need a new tech, he doesn't have a clue.

Now that I'm done ranting -- is the loud popping coming from the exhaust (out the prop) of back thru the carbs?

 

[Striper500]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

The Pop is coming from the exhaust, ie the prop.

 

[JUSTINTIME]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

timing is off
i would do a sync and link

if it came out the carbs, u have bad reeds

 

[Dhadley]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

Look closely at the plug wires and make sure they are on the correct plugs. I know it sounds silly but you have to start with the basics.

If those are OK then look at the primary (small) wire to each coil. They should be orange or orange with a stripe. If you don't have an OE manual tell us what color the stripes are and we'll let you know.

While you're there pop both wires off each coil and clean the terminals. Clean the ground on each coil too as long as you're there.

If all that's good, we'll need to pop the flywheel to check the key. If take the flywheel off, let us know before you put it back on. There's other stuff to check.

 

[Striper500]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

One more thing I forgot to mention about this. When I diagnosed the motor yesterday, I noticed that the spark plugs on the left side of the motor were clean and the right side were wet. (with fuel). Do these symptons imply something ?

 

[Dhadley]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

Were the port pistons dry and sooty? If so, those two are probably crossed.

 

[Striper500]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

I didn't get a good look at the pistons, but the plugs themselves were dry, and pretty clean actually. I just read some notes from the person who sold me the boat and it referenced a new CDI installed last year. Is it possible this might be wired incorrectly ?

 

[Dhadley]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

Might be. Depends on what he's calling a "CDI". That stands for Capacitor Discharge Ignition which is the entire ignition system type. We'll assume he's refering to the power pack for now.

Go back to my other post about the wires and the colors of the primary wires. Let us know what you find.

 

[Striper500]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

Today's summary. I started by putting new plugs, wires, and running a fuel line into a new clean tank to eliminate a lot of the easy stuff. After all that the motor still had the bad misfire. My next test was to check the timing. Cylinder 1 & 2 were already marked on the flywheel and appeared to be ok. It's when I went to cyclinder 3 I discovered the potential problem. It seems as though there is no spark going to cylinder 3. The timing gun would not light up, but did on cylinders 1,2,4. I installed a new coil on cylinder 3 and there was still no read on the timing gun. Just for kicks, I left the plug wire off cylinder 3, and sure enough the motor still sounds the same way - so I am virtually certain the timing guns assesment of no spark is correct. I was informed by the previous owner that the power pack was replaced last August. I did check the wiring, and it seems to be hooked up properly. Is it possible the stator is not delivering the current to the power pack to fire cylinder 3 ? In other words, there are plugs coming from the right and left side of the stator, each with 4 wires total. Are any of those wires cylinder specific ? is there a way to determine if they are working properly ? would it be possible that something is causing the old and new power pack to short ? One last thing. I pulled the plug out of cylinder 3 expecting it to be wet with fuel and it wasn't ? could this be possible, or may there be another problem at hand. Thanks Chris

 

[flabum]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

The stator simply provides the voltage to the pack, if the stator was bad, you would have no spark on 2 cylinders or no spark on any. if the pack was changed on that side, the fair assumption would be either a bad coil (switch it with a known good coil), a bad wire in the #3 circuit somewhere (check all electrical plugs and pins on that side of the motor between the pack and coil and pack and pickup coil) or a bad pickup coil (the part under the flywheel that moves with the throttle. The new pack could still be bad, simply switch them from side to side to eliminate that possibility.

 

[Mooney6959]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

I know that this is a VERY old thread, but did anything ever come of this?
I had my mechanic give the motor a once over and he said that everythign is good to go, but is still has this same misfire.
While mine is a '91 150, I figure the troubleshooting is still the same, my misfire just must not be as bad as his since I have 6 cylinders vs 4.
Anyhow, Anybody that can chime in for me would be greatly appreciated!

Thanks!

Another Chris

 

[CharlieB]

Re: 130 HP Johnson - 1995 - Bad Misfire - Need Help

Troubleshooting is exactly the same, just two more cyl's to test.

Verify spark on all cyls, swap coils, retest, swap boxes, retest, watch for the misssing spark to move with the part you switched to help identify the bad component.

Any question, start a NEW thread, explain what tests you have done and what changes you have found, one of us will response with advise.

Take Care

Charlie B