Top cylinder not firing Johnson 55ESL69A

[landgrj]

Hi all,

Took the boat of for the first time today after rebuilding the carburetors and setting the idle in the driveway. Got it out on the lake and it started up with the fast idle but always has a chug to it, not quite a misfire all the time but sometimes a complete misfire will occur.

Got it up to top speed (25mph) but had to take a slow ramp on the throttle otherwise it would bog down hard. After running it for 3 minutes or so in one lap i slowed down and it clonked out. Took 30 minutes to get it started again and then went back to the dock. On the way back in slow forward it was consistently missing and would die if i turned the throttle back too close to neutral.

Got it home and changed out the spark plugs to new ones, sounds better but still not a great idle and way to low without any fast idle. Decided to check the cylinders and if I pull the top spark plug there is no change in RPM or sound. Pulling the middle one kills the motor immediately and pulling the bottom one I can hear a large change and it sounds as though it is only on one cylinder and dies shortly.

I am not overly familiar with how the powerpack/coil/points interact to fire each cylinder. If only one cylinder is not firing where would any of those be a likely culprit?

Thanks,
Joe

 

[F_R]

I would first pull the flywheel and check the points/cut-out ring/etc.

 

[landgrj]

I checked the points and they were had a bit of carbon buildup on them. Cleaned them up and set the gap to 0.010". Engine seems to run better after that but I am still concerned that I am not always getting spark on the top cylinder.

Took it out and tested it on Friday and had it running ok, but noticed something that i find odd. On startup the engine doesn't like to idle well, rough and has a bit of a hard time going to WOT. Have to inch it along the first time, but after bringing it back down to idle it sounds great. The RPM is definitely higher after taking the throttle up and bringing it back to idle. Problem is as soon as I cut the engine and start it back up the idle is poor again. This seems very consistent in my testing (5-6 runs) of moving into forward gear and then pulling it back to neutral for a good idle.

Also tested spark today in the driveway with a inline tester that lets you set the gap. Got all 3 to finally spark with a .35" air gap. Top and bottom leads appear to be more inconsistent with the spark as well compared to the middle lead.

Next step is to follow the troubleshooting manual and test the coil and amplifier to see if I can determine anything. Any suggestions are appreciated.

Thanks,
Joe

 

[F_R]

I checked the points and they were had a bit of carbon buildup on them. Cleaned them up and set the gap to 0.010". Engine seems to run better after that but I am still concerned that I am not always getting spark on the top cylinder.

Took it out and tested it on Friday and had it running ok, but noticed something that i find odd. On startup the engine doesn't like to idle well, rough and has a bit of a hard time going to WOT. Have to inch it along the first time, but after bringing it back down to idle it sounds great. The RPM is definitely higher after taking the throttle up and bringing it back to idle. Problem is as soon as I cut the engine and start it back up the idle is poor again. This seems very consistent in my testing (5-6 runs) of moving into forward gear and then pulling it back to neutral for a good idle.

Also tested spark today in the driveway with a inline tester that lets you set the gap. Got all 3 to finally spark with a .35" air gap. Top and bottom leads appear to be more inconsistent with the spark as well compared to the middle lead.

Next step is to follow the troubleshooting manual and test the coil and amplifier to see if I can determine anything. Any suggestions are appreciated.

Thanks,
Joe

Is that a true statement? .35" is the same as saying .350" or a tad over 7/16". That would be excellent for that old battery CDI system. But if you really meant .035" (thirty five thousandths), that is borderline poor.

 

[F_R]

Is that a true statement? .35" is the same as saying .350" or a tad over 5/16". That would be excellent for that old battery CDI system. But if you really meant .035" (thirty five thousandths), that is pretty poor.

Well I screwed that up, didn't I? Corrected version above.

 

[landgrj]

Yes .350 is the measurement, so over 5/16. Glad to hear that is good, manual and others have said 7/16 to 1/2 it should jump so I wanted to check.
The amplifier was replaced in 2000.

Any thoughts on the idle being so much better after going into forward gear a bit and then coming back?

Thanks,
Joe

 

[F_R]

Maybe slack in the linkages.

 

[landgrj]

I checked the thermostat over the weekend as well thinking that maybe the engine never gets to properly warm up until going into forward and revving it up. It is working, opens a little late at ~155°F. Replacing it since it appears original.

Which linkages specifically F_R?

Also thanks for the responses, not sure how many people are familiar with these old motors anymore. Unable to find a shop near me that even wants to work on one anymore.

 

[racerone]

Your location ?-----Used parts may be easy to find.

 

[landgrj]

Live around the Milwaukee area of WI. I am going to look at the points again today as i know the surfaces of the points are not parallel. Not sure if that would cause this issue directly, but may as well see if I can adjust and fix.

Will also be doing a compression test today to have the numbers on hand.

 

[oldboat1]

Remove the plugs, and test each lead with one of these:

 

[landgrj]

I removed the lead from the plug and used one similar to that to do the testing for the above results.

Compression test was odd, engine would not turn over at WOT, i am sure there is a way around it but I didn't spend the time. Instead I opened the throttle plates by hand and turned over the engine. Got 115, 120, 120 from top to bottom cylinder (psi). Those numbers look good to me. The weird thing was it took many cranks to get up to those pressures, it was a slow climb all the way up, no large jump in pressure on the first turn over. Battery was getting real sluggish near the end of the 3rd cylinder test.

Also spent more time and re-gapped the points again after reading the Joe Reeves post on the different lobes and gaps. Now have them set to 0.009, 0.009, 0.010 on one point and 0.010 for the other point across the 3 lobes. Hoping that helps with the rough idle, going to try and start it in the driveway tomorrow to see if I can tell any difference.

Thanks so far for all the suggestions and keep them coming, enjoy learning about this engine as much as I can.

Thanks,
Joe

 

[racerone]

There is a safety switch on the engine block.----Prevents cranking when throttle is open too far.

 

[oldboat1]

plastic needle valve retainer might be worn (or missing), producing some idle mix variations.

 

[landgrj]

When I did the carb rebuild I put in all new plastic seats for the low speed needle.

Here is a video of it running in the driveway, sounds better than it did I think after re gapping the breaker points again. Still sound like an occasional misfire, maybe lack of back pressure?

Thanks,
Joe

 

[oldboat1]

Inline spark tester is not the same -- get an open air adjustable. No "plastic seats" for the l.s. needle. There is a plastic needle valve bearing in at the point of the needle. Plastic valve retainer is typically red and holds the needle in place after setting.

Can't do much tuning on muffs.

 

[landgrj]

carb rebuild was all new parts, replaced the plastic valve retainer as well. The spark tester is an open air adjustable as I showed in the photo attached to that post. Jumps a 0.35" gap in air.

 

[racerone]

Low speed mixture screws are set at how many turns out from gently seated ?

 

[oldboat1]

^^maybe too rich (chugs, stalls, hard to restart....)

 

[landgrj]

Starting from top cylinder low speed mixture screws:

Less than half turn (3/8 turn to 7/16)
Less than 3/4 (just under)
Less than half turn (3/8 turn to 7/16)

Operation of the boat is rough idle like above, but good once going full throttle and then coming back to idle it sounds great, significantly higher RPM.