Johnson 50 losses bottom cylinder intermittantly

[Rogerman]

I have a 2001 Johnson 50 (model J50PLSIG). For the last 4 trips (6 Months) this problem occurs when ever it wants to. Hot, cold, rough water, calm. Ihave changed the power pack and coil thanks to a friend. These did not help. Can swap the primary and secondary wires on the coil and get the problem to move. I checked the resistance on the Timer Base connector and got the following A to B 27 ohms, B to C 34 ohms. The manual says 27 + or - 5 ohms. As I've said, the problem is intermittant and as far as I know the engine was still running correctly. Any suggestions on how to verify that it is the timer base or some other component.

 

[clanton]

Re: Johnson 50 losses bottom cylinder intermittantly

If it is a 2 cylinder 2 stroke, check the VRO pulse hose, you will need to remove the starter to see the hose.

 

[ICEMAN]

Re: Johnson 50 losses bottom cylinder intermittantly

You mentioned that when you swapped the primary and secondary wires, and the problem moved. This would lead me toward an ignition system problem. Is this a two or three cylinder, 2 stroke? not that it matters much. Try this- find top dead center of #1, #2 and #3 if it's a 3 cylinder. Mark the flywheel, with a white coloring, (Paper Correction fluid works well.) Put a timing light on each cylinder and see if the correct marks lights at TDC. If you see 2 marks at the same time, you have a doubling firing problem. Usually it's a power pack. When the light flashes,and you move it around on the flywheel, you would see the other cylinders, but not at TDC. In any event if you see more than white marks, than the number of cylinders, you have a double firing problem. Also check the plugs in the wiring, moisture in one could cause a misfire.

 

[Rogerman]

Re: Johnson 50 losses bottom cylinder intermittantly

Sorry about the time. Been traveling on business and haven't had time to work on the problem.<br /> <br />Clanton, it is a 2 cylinder 2 stroke. Just curious, why the VRO pulse hose?<br /><br />Iceman, what else besides the Power Pack. Have used a known good power pack and coil with no success. These are back in a friends motor and running fine.

 

[clanton]

Re: Johnson 50 losses bottom cylinder intermittantly

Because just about every one of those engines the starter rubs a hole in the pulse hose, the hole causes the lower cylinder to mis fire, lack of fuel. If the hose has a hole, replace hose, grind notch in starter base. Has nothing to do with ignition. When you check the ignition system, its inportant to check the output voltage of of the stator, pack, timer sensor, and you are out of spec on B to C. When you did the ohm test you only did 1/3 of test requied in service manual. Recheck the timer, disconnect tan wire to pack and try it.

 

[Rogerman]

Re: Johnson 50 losses bottom cylinder intermittantly

Clanton - Had a little time to look at the motor today and as you promised, the starter has worn a hole in the VRO pulse hose. I will replace this. Since I'm very new to outboard engines, why would the VRO pulse hose only affect the bottom cylinder. It wasn't obvious by looking at the engine?

 

[clanton]

Re: Johnson 50 losses bottom cylinder intermittantly

It is only connected to the lower cylinder, causes the lower to run realy lean,will ruin cylinder if not repaired. It runs lean because it sucks air thru the hose instead of fuel thru the carb, also fuel pump will not pump to specs.

 

[rudeafrican]

Re: Johnson 50 losses bottom cylinder intermittantly

Great job of diagnosing the problem there Clanton, I'm impressed. Never tires me to see an expert at work. Keep it up.

 

[clanton]

Re: Johnson 50 losses bottom cylinder intermittantly

Thanks, but someone else showed me the first one, just about ever 40/50 2 cylinder that year has that problem. Its a quality control problem.

 

[Joe Reeves]

Re: Johnson 50 losses bottom cylinder intermittantly

Roger..... You say that you've changed the coil and powerpack but encountered no change in the problem. However, when you switch the primary leads to the coils (using the top coil to fire the bottom cyl & vice versa), the problem transfers to the top cylinder. This indicates that the problem is electrical (ignition) as you've done nothing that would affect the fuel routing.<br /><br />Since the problem changes positions (cyls), this eliminates the coils, s/plugs, and powerpack since you have already changed them, which leaves the stator assy and sensor, along with their associated wiring.<br /><br />If the powerpack had not been changed, it would be possible for it to be the problem, but it is highly unlikely that two powerpacks would have the same exact problem.<br /><br />The clue to your problem is the word "intermitent" which could be related to a frayed wire connection at one of the pins or sockets within any of the wiring connectors, or even simply a dirty or loose pin/socket. It could also be a frayed wire leading from the timer base to the powerpack which would short out against the block etc at times, or set up a make/break situation.<br /><br />The stator which supplys AC power to the powerpack will affect the ignition if it starts to fail, but that usually affects all cylinders on your model engine. However, I'd suggest that you take a ohm reading on that item just to eliminate it. Let us know what you find.

 

[Rogerman]

Re: Johnson 50 losses bottom cylinder intermittantly

Just like to thank everyone for the help finding the problem on my motor and thanks to Clanton for pointing out another potentially serious prob. I also found a few other hoses that had wear marks. The actual intermittant probelm turned out to be a bad wire on the trigger assy. (Ouch on the price) Again, thanks to everyone.