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1999 35hp Johnson engine trouble

T

TexasA&M

Member
Howdy folks -

I have a '99 Johnson 35hp 3 cylinder engine that is giving me trouble. This weekend, I was out throwing the cast net while my buddy idled us around. After about 10 minutes, the motor quit running out of the blue. Wouldn't restart, so I used the trolling motor to get us back to the house. It would fire every once in a while, but wouldn't start. It acted like it was flooded. After I got home, I shot some starting fluid in the carbs and it fired right up. Went out again, and it started sputtering again. Got it running with the starting fluid and she made it home. I pulled the plugs and they all look great. I drove the boat around a bit yesterday and today and it didn't leave me stranded, but I didn't go too far from home either.

Another weird thing it's doing is missing at speed. It'll be running along fine at wide open and then it will skip. You can hear and feel it when it does it, but then she just keeps running.

Any thoughts on what my issue is? It's almost like it's starving for fuel, but I don't know why. I just bought this motor from a dealer that had gone through it before listing it. Everything looks to be in good shape, but obviously something is amiss. Unfortunately, the dealer is out of state, so I can't work back through them.

Let me know what y'all think!

Thanks,

- Steve
 
Model is J35TEL3EEM.

As far as pumping the bulb, I've done that when it acts up at slower speed, but at wide open, I'd basically have to just keep pumping the entire time I'm moving. I'll give that a shot this next weekend though and see if it makes any difference.

Overall, I like the way the engine drives; it is easy to start (with the one time being the exception), runs smooth and quiet, etc. I'm not impressed with the performance (it doesn't push my boat any faster than the 25 it replaced) and now I don't trust it to get me around the lake. It also burns twice as much fuel.... I'm going through 5 gallons a day it seems, and that's with really not much use.
 
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Hopefully the oil injection has been removed and thrown away.------Start with a compression test.--Compression results from last week are not valid today.--Then a spark check.---Spark MUST jump a gap of 3/8" or more.-----Test run with cowling of at night to see if spark jump to ground anywhere.
 
No oil injection in site on this one. Not sure if it ever had one though because I haven't seen any mention of that system in all of the schematics I've looked through.

Not sure I understand the spark gap.... Are you thinking that I'm sparking somewhere other than the plugs?
 
??----Those 3 cylinder motors came with oil injection.----It was not a reliable system and has likely been tossed in the garbage !------Spark must jump a gap of 3/8" or more to be called good.----Sparkplugs are not used when doing that test.-----And yes the spark can jump from the plug boot to ground.----Some simple testing on your part can save you some coins !
 
Note-----The oil tank is shown with cylinder & crankcase.-----Mixing unit is shown with fuel system parts.----All very clear !
 
Sure enough! I see the oil system now. It has definitely been removed from my unit. How can I tell if it has been done correctly? She's been running good on mixed gas, so I assume everything is good to go, but maybe something is amiss?

How do I check the spark gap? I'm all in for some simple testing!
 
The question is very clear I believe.---So, does spark jump a gap of 3/8" or more , yes or no ??----There is no mention oi the motor running in this question.
 
What I was finding at first was a spark tester that showed spark as the motor was running. After a little more digging, I found the right tool and will be picking one up or having Amazon deliver. I'll check it out as soon as I can and go from there.
 
Dang, didn't think about the prop being different. I'll check that out tomorrow when I am testing the spark. The previous owner could have put a lower pitch on this motor for whatever reason.

What's the best way to measure WOT?
 
Easy enough! I'll get one and check it out this weekend. What should WOT be on this motor? I haven't been able to find general specs on this motor anywhere.
 
Compression was even at 125 across all three cylinders. Sparked jumped a 1/2" gap across all as well. I switched props out with the other motor and there wasn't any noticeable improvement in speed (I used a speedometer app on my phone; I seemed to gain a mile an hour or two, but I was running lighter than before as well). The tach arrives on Thursday, so I'll be able to measure WOT this weekend.

Pumping the bulb seemed to help with the cutting out at WOT, but I'm not sure if it was coincidence or not. I ran around for 15 minutes or so and then stopped at the house to unload a few things. Jumped back in to put it back in the slip and it died while idling and wouldn't restart. The tank is low on gas, but the primer bulb was full, so I don't know what the issue is.
 
I found a document online yesterday that showed 5,200-5,800rpm, so that's what I'm going with.

What should I check next to help diagnose my issue? This thing is worthless if I can't trust it to run for more than 10 minutes...
 
What are the slow speed mixture needles set at ?------1-1/2 turns out ?---Or the distance as specified in a factory manual ?
 
Per the dealer that I bought it from, they are set to factory specs. I have not verified, however.

Would a bad adjustment here allow the motor to run seemingly fine for 20 minutes and then die without being able to restart?
 
I'll see if I can find another tank and hose set up. Theoretically, I could just put a hose down in a gas tank because the pump will draw.... I don't have to have a pumper, right?

Speaking of, I went out tonight and tried to start it.... she fired right up without pumping the bulb, so I know it wasn't out of gas yesterday.
 
I'll see if I can find another tank and hose set up. Theoretically, I could just put a hose down in a gas tank because the pump will draw.... I don't have to have a pumper, right?

Speaking of, I went out tonight and tried to start it.... she fired right up without pumping the bulb, so I know it wasn't out of gas yesterday. I verified that there are no errant sparks as well (ran it in the dark and looked it all over).
 
This is another Optical Ignition engine so it needs QL82YC Champion spark plugs only. No NGK. They interfere with this ignition system. Can cause irratic running. Just something to consider. Next time it won't start check fire immediately! If it cools off it will come back. That will usually be a pack.
You might also look at the little recirculation lines up against the block (starboard side) behind carburetors. The originals disenagrate. Get some yellow tygon tubing like used on weed eaters to replace if necessary.
 
I verified the other day that these are the Q series champion plugs. I'll keep the spark checker on the boat and test it immediately next time it dies out. That said, the last time it happened, I got it restarted with starting fluid...

I'll inspect the lines this weekend. Everything looked pretty good when I pulled the powerhead off a few weeks ago, but I only gave it all a once over and didn't do any deep inspections.
 
The little recirculate lines all look good. No leaks, all feel firm and solid, and nothing came off when I gave them a slight tug.

As for the mini tach, how often do these engines spark per rotation? I set it for 1 spark per rotation, and it says that it's idling at ~3000 rpm. I went through all available settings and could never get it to read correctly. Right now, I've got it on the 2 spark per rotation setup, and it reads ~1,800 at idle. I figure I can just divide the number by 2 to get the real reading when I lake test it tomorrow.
 
I am suspecting you have a flaky power pack, but I hate to guess on such an expensive part ($400 here). Cheaper after market alternatives on eBay, but I have no experience with them?

I have not used the Mini tachs. Maybe others can comment on how to hook up. I do know that irratic firing is a symptom of this ignition system failure. If you have a timing light it would be interesting to see if the light looks constant when the engine runs poorly. You also have a sensor, but the ones I have fooled with ( including my own motor) have been packs so far.
They are good little motors, but heavy for the horsepower. Mine has TNT with the tiller so it is really heavy. The motor does have a rev limiter. I believe it is about 6100 RPM. (May be coded on the pack.) It would cut out & be like a miss at that RPM, but have no bearing on hot restarts or any running issues below limited RPM.
 
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