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2003 Johnson J25RSTC milky fuel/oil, rough idle, hard start

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hennessyktm

New member
After much googling, forum searching, etc. decided to post. Picked up a 2003 Johnson 25 J25RSTC from an older gentlemen who said he was tired of fooling with it. It was hard to start, would run and idle rough. The guy said the fuel pump cover was cracked so he replaced it. Blamed this for the poor running admm said the carb probably just had to be cleaned. Current status: Compression is 101 and 106 psi cold, throttle wide open. Excellent spark on both cylinders. Hard to start, idles rough, and I get quite a bit of milky/oily fuel residue all over the outside of the midsection and lower unit after running it in a barrel, and, asmall puddle of the stuff on the garage floor after running it/leaving it sitting. It oozes this milky fuel/oil out of the top weep hole in the lower unit - this is not gearcase oil, it is fuel/oil/water mix...stinks like gas. The spark plugs are WAY too clean when I pull them, almost spotless except covered in gas. I assume unburnt premix is "cleaning" them rahter than detonating and leaving some soot/black/tan color. I have changed the waterpump, gearcase oil, driveshaft seals, rebuilt/cleaned the carb (new float, float needle, needle seat, gasket, set float so it is parallel with carb body when turned upside down), reset the air mixture screw to 1.5 (now 2) turns out, adjusted the throttle cam roller so it is between the 2 timing marks of the cam when the carb butterfly just starts to open, and adjusted the idle screw so it is making contact with the throttle stop and idling. I am thinking one of the following, or a combo:
  • the fuel pump is somehow delievring way too much fuel
  • the float is allowing fuel to bypass/get into the combusiton chamber
  • the timing is WAY off
  • the lower crank seal is shot. Really hoping it isn't this.
Can the intake reeds/intake manifold be at fault here? Any other ideas or suggestions? Service manual should be here in a week or so. Looking forward to your thoughts and advice.
 
Outline your starting procedure.----Do you operate the manual primer found on the motor ??-----Checked the flywheel key ?---Thermostat checked ??----I do not like those compresson numbers.
 
Welcome to the forum. The cylinder that operates the fuel pump may be sucking fuel through the pump diaphragm. This will be determined by the presence of fuel in the port that connects the vacuum/pulses between the block and the pump. If the guy was fighting problems, this could have been the cause. Kits are inexpensive and fun to install.
 
Thanks for the reply. Starting goes something like:

  • ensure the fuel vent on the gas gan is open, shake can
  • pump primer bulb on fuel line until hard, pull primer on front of motor once or twice
  • turn/open throtte to start position
  • pull starter cord
Have not checked flywheel key of thermostat. Will look at these, thanks.
 
Good call on the cylinder sucking fuel, I will check this. I was just out in the garage troubleshooting the motor after watching a guy's video where his 25 Johnson's primer was stuck open and flooding the motor with excessive fuel. Troubleshot this about a half hour ago. The primer on the motor doesn’t seem to be the problem; but found the following:

  1. Bottom cylinder is either not firing or intermittently firing. I removed the top cylinder’s plug wire, the motor died. Started it back up and removed the bottom cylinder’s plug wire – no change. Motor kept running, rough.
  2. Also pulled the spark plugs and the top cylinder looks milky. Can’t quite tell if this is fuel or water this time. I am really hoping it is fuel and the problem is as mentioned with the top cylinder pulling fuel from the carb. I’ll re-check and post back.
I feel like I need to time the motor and potentially buy a coil and new head gasket head cover/water jacket gasket. While in there, replace the thermostat.
 
Now THAT reply above ^^^ (sea turtles) is quite reply to a motor problem, lol.
Only other update, both coils pass the spark gap test @ 7/16".
Onto the fuel pump and fuel pump vacuum and timing.
 
Milky spark plug indicates water is getting into cylinder somehow. That is serious, and must be addressed, if it isn't too late.
 
Lower crankshaft seal is difficult to diagnose.----Often folks will clean carburetor 3 times .----Replace coils and powerpack.-----Fuel pump .----All in desperation.------I would inspect the lower crank seal.-----Not saying it is the issue , but not hard to remove powerhead and inspect it.
 
I am definitely going to check the lower crank seal, but also want to check the timing. I really want to wait to knock both of these out until I receive the service manual, which is still on its way in the mail. According to the Joe Reeves timing method I read about, timing at idle should be ~4 degrees retarded from WOT. WOT timing is 30 degrees before top dead center on this motor. When idling in the test tank, with the timing light clip on the top cylinder's spark plug wire, which I believe is cylinder #1, the timing is so far off there are no timing numbers/tick marks beneath the timing light when it flashes. It is literally firing on the opposite side of the flywheel where is should be firing. I tried to post pics from google photos, but can't. I'd be happy to email them to anyone who can help troubleshoot! Thanks for all the posts and suggestions thus far.
 
About the only thing that will change the timing is a sheared flywheel key.-----And no , you can not use a timing light to check for that.----And timing is set at the factory for the life of the motor .----Simply does not wear or go out of adjustment.
 
racerone said:
About the only thing that will change the timing is a sheared flywheel key.-----And no , you can not use a timing light to check for that.----And timing is set at the factory for the life of the motor .----Simply does not wear or go out of adjustment.
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A few days ago I checked - the flywheel key is in place and in tact. I am aware timing is set at the factory and doesn't wear out/go out of synch with use, but this engine did have the head previously replaced and I am unsure if the PO/mechaninc screwed something up or not. I just want to rule timing out as a possibility. the first thing I did when I picked up the motor was replace the WP, and I was surprised to see the WP housing, driveshaft, etc. covered in a nasty oily residue. It didn't smell like gas at the time, so I figured the driveshaft seals were bad. I replaced them, only to discover this huge overfueling issue....wasn't the driveshaft seals.
 
fdrgator said:
Sensor wires reversed. Or coil wires reversed.
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Was thinking the same thing. I am half thinking I'll swap the plug wires and see what happens...if they'll reach. If not, may throw on some motorcycle plug wires I have laying around and see how it repsonds. hope the longer plug wires/additional resistance won't cause further issues. I'll report back shortly...
 
Just an update...
I went ahead and ordered a new thermostat and gasket, head gasket, water jacket gasket, and water diverters for the motor. Figured I'd pull it apart and replace, if nothing else, for good measure and to rule this/them out. Did it last night, so glad I did, as this was definitely a huge problem. The thermostat was trashed and stuck open, a chunk was missing from it. The head gasket was leaking water into the cylinders - more so the top cylinder than bottom. It was hard for me to tell if it was water or fuel since the plugs were covered in fuel, hence, stunk like gas. It was blatantly obvious when pulled the head, milky mess. The head gasket was leaking between the 2 x cylinders, this is why I believe I did not have seriously low or alarming compression numbers - one was just leaking into the other. The water jacket was a salty mess, but cleaned up nicely. So did the head, bolts, etc. The head looked flat/true, but time will tell if it is warped and needs replacing. I conducted another link/synch and adjusted the low speed screw. Starts right up and idles, but I still get a cough from the motor intermittently. I do not believe it is a fuel issue and may be ignition related. Still have to troubleshoot this. I also want to do another compression test to see if there is any difference, but I'd assume the numbers will be similar to the previous test. I also received the servie manual I ordered (NOS), and was surprised it does not have compression numbers in it and only states the 2 cylinders should not vary more than 15 psi. Lastly, no more milky fuel/oil leaking from the lower unit, only water.
Any suggestions on the cough/skip at idle? I really don't think this is fuel delivery, as I've cleaned the carb, set the float, etc. and confirmed several times now, and also have a new fuel pump installed.
 
Every cylinder head I have looked at has been warped to some degree !!----And try opening low speed mixture screw 1/8th turn at a time and see if low speed cough goes away.
 
Thanks for the reply. I already adjusted the mixture screw. I started at 3 turns out in accordance with the manual, then screwed it in until it ran rougher/coughed, and backed it out 1/4 turn. I believe something else is causing it to skip/cough/stumble.
 
Maybe throttle plate is opening too soon or NOT closed at idle.------It is one of those adjustment that looks wrong to a novice.----When in fact it is correct !
 
Throttle is definitely NOT closed at idle. I find the synchronization and linkage adjustment a little confusing, here is why:

  • Step 2 states "loosen locknut and back out throttle arm stop screw until throttle arm touches screws mounting bracket." The only way to get my throttle arm to touch the bracket is by removing the throttle cable anchor and screwing the throttle cable into the throttle arm bracket about ~10 turns. This ends up causing an incorrectly adjusted throttle cable, as the manual states there should be 2 inches/50mm +/- one turn between the anchor and end of the cable sleeve.
  • I did adjust my throttle cable to allow the throttle arm to touch the bracket, and then did the synch and link. What ended up happening is there was not enough adjustment in the throttle stop screw (aka: idle adjustment screw) to bring the rpms up for the motor to stay running/idle. I ran out of threads/adjustment - the screw was bottomed out in the adjusted.
  • So, I adjusted the throttle cable back to spec and then did the synch/link. I used a throttle shaft amplifier to the carb throttle shaft, and adjusted in accordance with the manual. The carb throttle plate begins to move just when the roller is between the two marks. Great, however, I had to turn the throttle stop screw/idle screw in to get the motor to idle. No biggie, but now, at idle, the butterfly is not fully closed and the roller is passed the two timing marks. Again, the roller begins to open at the proper time, but the motor only idles when adjusted like stated above.
In summary...currently throttle cable is correctly adjusted (2"/50mm), butterfly fully closed with thorttle closed, butterfly is fully opened at full throttle, but had to turn idle screw in to get motor to idle, which has the butterfly opened a little bit/not fully closed and the roller to be passed the timing marks on the cam at idle.
You may be onto something, but am unsure which procedure to follow due to conflicting guidance in the service manual.
Thoughts??
 
If throttle plate is NOT closed at idle , your engine will not idle.----I could likely fix that issue in minutes.----But I do not want blisters on my tongue or fingers explaining how to correct this !!
 
racerone said:
If throttle plate is NOT closed at idle , your engine will not idle.----I could likely fix that issue in minutes.----But I do not want blisters on my tongue or fingers explaining how to correct this !!
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racerone, I guess I'll start researching "won't idle with butterfly closed." Too bad you aren't my neioghbor, lol. Any good references, video links, etc. you know of? I'll dig into it after work this evening.
 
hennessyktm said:
Tracking, but really hoiping this isn't it. Will explore this as last option.
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Following up, I am confident it is the lower crank seal. I was thinking it may be the power pack, but it starts right up now, has great spark, seems to be timed correctly at idle (I know, you can't check timing at idle, etc.); but the motor passes the cylinder index/timing check in accordance with the service manual. I believe me having fooled with it for so long has provided the lower seal to partially function, idea being it has been saturated in premix/oil for the past few weeks and is now able to seal...barely, at idle. I believe the seal fails with any application of the throttle. Here is why:

  • Starts, idles fine. Revisited the sync, linkage, idle air screw, and carb float for the billionth time. Miraculously, finally got it to idle w/ carb butterfly fully closed. No significant changes to what I had been doing…following the service manual.
  • While idling, if I give it any throttle at all, it will start to backfire/miss.
  • When under throttle and the motor backfiring/missing, if I take my fingers and restrict some of the airflow entering the throat of the carb, the engine will run fine.
My theory is that applying throttle increases vacuum and crank pressure, exceeding the capability of the old, brittle, saltwater abused motor that had been left sitting for years on end.
I wish it was the carb, as it is an air/fuel problem, but I don’t believe it is the culprit. This carb is the easiest carb I’ve ever worked on and kind of hard to screw up. Everything in the carb is correct in accordance with the manual. About to pull the trigger on ordering what I need for the crank seal unless someone sees a glaring issue with my analysis and can provide me a helpful alternate perspective/thought.
Appreciate the feedback thus far.
 
Maybe throttle plate is opening too early.----At idle look at the rod on the port side of the motor.-----And is there a gap between the adjustable stop and that plastic piece.-----Read carefully and answer.
 
racerone said:
Maybe throttle plate is opening too early.----At idle look at the rod on the port side of the motor.-----And is there a gap between the adjustable stop and that plastic piece.-----Read carefully and answer.
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Yes, at idle, there is a gap between them. The buttrerfly operates exactly like described in the service manual, with the throttle linkage/butterly begining to move when the roller is between the two timing marks on the cam.
 
when you cleaned your carb did you take the orfices out,did you take out the 2 core plugs and make sure everything was open.you said if you restricted the airflow with your fingers you could make it run which leads me to think its a fuel problem.if you put several fingers over the carb throat can you feel it suck you fingers against it,if thats the case i wouldnt think its the crankcase seals.
 
stork55 said:
when you cleaned your carb did you take the orfices out,did you take out the 2 core plugs and make sure everything was open.you said if you restricted the airflow with your fingers you could make it run which leads me to think its a fuel problem.if you put several fingers over the carb throat can you feel it suck you fingers against it,if thats the case i wouldnt think its the crankcase seals.
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Thought I posted a reply a while ago, don't know what happened. When I cleaned the carb, I took out the drain plug and orifice in the bottom of the bowl (hihg speed, I believe), needle, needle seat, orifice on the face of the carb (low speed, I believe), and low speed air mixture screw. I tried to takeout the needle looking emulsification tube, which sits in the location where the throttle needle is on a motorcycle carb, but it was stubborna nd I did not want to damage it. I confirmed air and carb cleaner passes through each jet, orifice, and passage in the carb; even creating a pubble in teh roof of the carb with the carb upside down to ensure the carb cleaner drained through thos holes. Also ensure the fuel inlet, primer inlet, etc. were all clear and albe pass air and carb cleaner.
When I have it running at idle, it is fine. As soon as I give it a little throttle, it starts to backfire/sputter out of the exhaust/prop. If I place three fingers gently over the carb intake while running and givng it throttle, you can feel the carb pulling air through the intake, trtying to suck your fingers in as expected, and I can give it throttle without it backfiring. This is why I think it is a lower crank seal.
 
My guess is-----Throttle plate opening too early.-----But I can not see , hear or touch your motor.----Up to you to repair or visit your local friendly repair shop.
 
racerone said:
My guess is-----Throttle plate opening too early.-----But I can not see , hear or touch your motor.----Up to you to repair or visit your local friendly repair shop.
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It isn't. I adjusted it and checked/re-checked it a billion times in accordance with the service manual. It is spot on. I think it is the lower crank seal. No way in hell I am taking it to a repair shop.
 
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