85 Johnson WOT Issue

[Jmcjunkin3]

I am! I'm just glad I finally found a "smoking gun". Chasing an issue with no results day after day was getting tiring. And again, thank you all for your help and patience!

 

[Jmcjunkin3]

Alright guys, so I got the parts and installed them saturday. Topk the boat out yesterday and it ran worlds better, definitely hitting on all 4. Well, when we put the boat away a few years back, it had an intermittent misfire at WOT, where it would drop a cylinder for a few seconds then come back in full strength. Well, it did this again this time, BUT after an hour or so, it totally laid down and ran on 3 for the rest of the day. Still plenty of power to get up on plane but not full speed. I'm gonna read the plugs after work sometime this week, but I had a lean sneeze on cyl4 last time I looked so the culprit may be there. Just wanted to keep everyone updated and maybe get some suggestions for what I should test for. Right now I'm going to read the plugs, check spark again, and check signal coming from the power pack. Thanks in advance!

 

[interalian]

Could be just a coil now. I had a coil fail and it ran like crap on 3, like half power surprisingly. Do a spark test when it fails, or use a timing light to check for spark problems one cylinder at a time - best when it's acting up.

 

[Jmcjunkin3]

yup one of the plugs should definitely tell the tale but we'll see. If it's a coil, that's fine with me...at least it'll finally be fixed. just odd because it's had the same intermittent miss for years, then finally laid down completely yesterday. thanks for the advice.

 

[Jmcjunkin3]

Alright, I finally have some updated results for you guys. So I tested spark before I hit the river Saturday, all good there. But...same results. Took the spark plug boot off of #4 and sure enough it ran exactly the same. Dead hole

I'm starting to suspect it was a failing reed valve that finally let go. Let me know what you all think. Thanks again!

 

[jimmbo]

When it is running, with the air silencer off, spray some gas oil into the associated carb. Is it inhaled, or is it spat back out? Spitback is one symptom of a reed problem. If the engine suddenly speeds up, then you have a plugged up carb circuit

 

[Jmcjunkin3]

Good idea...when it was firing on that cyl, it was spitting out on that cyl, which is why I'm suspecting reeds. I will definitely run that test before I tear the motor apart though!

 

[Jmcjunkin3]

Hey guys so....I'm fairly certain i found the issue and I feel really stupid but I can't help but share because it's also funny. I did a lot of reading and the symptoms I've been experiencing matched up so well with a bad reed valve that I went ahead and pulled the intake manifold today after work. Well, as you can see, they were all in tact and clean as a whistle. So...I took the high speed jet out of the carb on the dead cyl and sure enough....there was a piece of insulation from the hood stuck right in it. I was so confident in how I had cleaned the carbs that I didn't consider than foreign material can always be sucked in. So that complains the complete loss of that cylinder. What it doesn't explain, however, is how I had that intermittent miss years ago at WOT and how it was still doing the same thing all these years later. This leads me to believe a bad coil or powerpack is still present somehow.

https://drive.google.com/open?id=0B62Fyxg1VzwYVnpoeFNVRzdCRTQ

https://drive.google.com/open?id=0B62Fyxg1VzwYNDRPbGJTT2pTWFk

 

[jimmbo]

I hope the plugged jet hasn't starved the cylinder of lubrication, no fuel equals no oil. You were trying to run it at full throttle

 

[cfauvel]

can you move the suspect coil to another location to see if the problem moves to new location?

 

[Jmcjunkin3]

jimmbo, it wasn't run too long so I'm thinking it should be okay. cfauvel, that will be my next step. I have replaced 2/4 of the coils and I'm just about ready to go ahead and do the other two, but I'm going to try switching them first. If it's a power pack...well...so be it.

 

[Jmcjunkin3]

Hey guys! I know it has been awhile and I apologize...to make a long story short, I diagnosed my power pack being bad due to the fact that I couldn't get spark on cyl 3 no matter what coil I put there...replaced the power pack and now it's back to being intermittent....until last night when it basically completely laid down again...something odd I noticed- at full throttle it ran only on 3, but if I backed off the throttle ever so slightly, #4 tried to come in and fired intermittently. I am absolutely stumped at this point, any suggestions would be great. Just for a recap I have-

replaced the coils, power pack, timer base, rectifier
cleaned and greased the new timer base, rebuilt the carbs, did plugs, checked the reed valves, new fuel lines, new fuel pump, seafoamed, basically everything. I've been through this motor top to bottom. please help!

 

[cfauvel]

I'm stumped...have you tried swapping plug wires? maybe reduce the gap of the #3 plug for testing purposes?

 

[Jmcjunkin3]

Yessir. Once I have time I'm going to check spark with my spark tester again now that the problem is back. If I have consistent spark on the tester then I know to close up the gap...sigh.

 

[Jmcjunkin3]

Alright guys...I tested spark again on the troublesome cylinder and I noticed that the spark was pretty orange and unhealthy. Cleaned up the grounds very well and tested them all. I now have a nice blue spark on that cylinder...could that have been the issue? Seems pretty likely but I'm not holding my breath over here. Also took the flywheel off again and cleaned the timer base off and greased it again as well. Guess we'll see tomorrow, most likely the last trip I'll be taking on the boat this season. Thanks for everything guys, if anybody thinks of any other diagnostic tools please let me know!

 

[aspeck]

Hope this take care of it for you!

 

[cfauvel]

Alright guys...I tested spark again on the troublesome cylinder and I noticed that the spark was pretty orange and unhealthy. Cleaned up the grounds very well and tested them all. I now have a nice blue spark on that cylinder...could that have been the issue? Seems pretty likely but I'm not holding my breath over here. Also took the flywheel off again and cleaned the timer base off and greased it again as well. Guess we'll see tomorrow, most likely the last trip I'll be taking on the boat this season. Thanks for everything guys, if anybody thinks of any other diagnostic tools please let me know!

I would say that YES an orange spark could very well be the culprit....with the sparkplug in the chamber, I believe the resistance is greater as the pressure increases, so a weak orange spark at sea level (outside the chamber) will be even worse under pressure....anxiously awaiting results

 

[Jmcjunkin3]

Hey guys, sorry for the delayed response. I had quite a time on the river this weekend, between fixing the boat and then putting a starter in my truck in the launch parking lot yesterday...so I launched the boat and I didn't feel much of a difference. Pulled the plug wire on cyl 3 and sure enough that was STILL the culprit. I finally got done with messing around and pulled the lower carb ON THE WATER. Not an easy task to do while the boat is rocking but I've had them off a few times so it didnt take too long. Just as I had expected, a small piece of debris was clogging the high speed jet on that cylinder! (I had forgotten to mention that I had a little issue with some water getting into the motor, must have come from there) cleaned out the jet and it ran PERFECTLY....for all of about 10 seconds. Cleaned it out 2 more times after this and it's been singing at full RPMs since then. Absolutely ecstatic. Just a shame that I finally got it running perfectly on my last trip, but oh well! It'll be all ready for next season and that's really what my goal was. Thanks to all for all of the help and support!

 

[cfauvel]

But where is the gunk that is getting into the hi-speed jet coming from?

 

[interalian]

But where is the gunk that is getting into the hi-speed jet coming from?

I've not re-read the thread, but would suspect decaying fuel lines after the pump, assuming the filter screen is intact and its gasket is OK.