77' Johnson 25 cuts out, runs rich

[DavidT]

I'm having a problem with a 1977 Johnson 25. Unit runs and has a distinct miss and coughing at idle and under load. Plugs are wet fouled after a few minutes of running. The unit requires a hell of a rich mixture to run in length of time. 4.5 to 5 turns backed out on idle screw. Exhaust so rich it burns my eyes. I've changed two secondary coils. The original plugs that my father-in-law had were Champion J4C gapped at probably 0.020", I changed to 0.040" per the clymer manual (but wrong recommended plug) and the unit idled pretty good with an occasional miss that was regular under load. I put the Clymer recommended QL77RC4 gapped at 0.040" and NGK recommended (4122?) gapped at 0.030" and unit ran like crap, missing and coughing. I took carb apart and checked for wronk float level, pulled idle screw out and looked inside...carb is extremely clean with no apparent faults. No raise in engine rpm when sprayed with WD-40. Was thinking the CD2 Power pack bad but now I'm leaning towards air leak, but both plugs are wet when removed. Any thoughts greatly appreciated.<br /><br />Thanks,<br /><br />DavidT

 

[DavidT]

Re: 77' Johnson 25 cuts out, runs rich

TTT<br /><br />Any helper's out there.<br /><br />Thanks,<br /><br />David T

 

[alcan]

Re: 77' Johnson 25 cuts out, runs rich

Hi David<br />Remove the carb again and check the condition of the main nozzle gasket. It's between the bowl and nozzle, It's round and has three nubs on the inside. If it's missing or in bad shape it will cause a problem like you describe. The champion QL77RC4 at 0.40 should work fine. I would think an air leak would cause a lean condition. With all the smoke and wet plugs it sounds as you have a fuel control problem (too rich). You stated that you checked the float level and it was correct. Did you also check to see if the needle and seat were shutting of the fuel? Might be some goop in there. You may also have a pin hole in the fuel pump diaphram, helping flood the cylenders. Can I assume your running fresh fuel mixed at 50:1? Are fuel lines,connectors,primer bulb in good shape?

 

[DavidT]

Re: 77' Johnson 25 cuts out, runs rich

I was wondering if someone could tell me how the tiller handle operates the timing advance when everything is operating properly. The throttle gears where they 90 degree up throught the engine cover had a lot of play in them. I loosened the one gear and pryed it closer to the other gear which took a lot of the slop out of the controls. My question is, if you look at the cam follower with the tiller handle in the full clockwise (slow) position, my engine seems to vary the position the cam follower contacts the stator advance mechanism. Usually it falls between the two marks or sometimes a 1/4" to the right of the two marks. I am wondering if the ignition timing is changing causing my missing and coughing problems?<br /><br />Thanks,<br /><br />David Thomas

 

[alcan]

Re: 77' Johnson 25 cuts out, runs rich

Hi David<br />If You follow your manual step by step and check and elimenate each system, You will find the cause or causes of your problem in short order. The first thing to check is compression (with a gauge) get real numbers. The finger in the hole routine is for the birds. If this tests ok, then move to the ignition system. The only way your motor can be out of time is if the flywheel key is sheared or half sheared or the key way is buggered up. Pull the flywheel and look for signs of rubbing,loose components,loose stator plate,etc. Test acording to the book. When all is tested good and you have a nice spark to both plugs. Go to the fuel system. Follow the same step by step procedure.Once this is cleaned and properly adjusted. Then check the syncronizing as out lined. If you aproach this in a linnier fashion you will get there quicker. The linkage from the tiller to the stator plate has little to do with any thing,it just turns it.The important part is the linkage beteen the carb and the stator plate. Check that the cam follower is not real worn or missing. Keep us posted on your progress. Don't hesitate to ask more questions. Good luck.

 

[DavidT]

Re: 77' Johnson 25 cuts out, runs rich

Alcan, Thanks for the information, the cam follower is worn and has a flat spot on one side of the roller. I am in the process of purchasing the roller at a Johnson dealer here in town.<br /><br />Thanks,<br /><br />David Thomas

 

[DavidT]

Re: 77' Johnson 25 cuts out, runs rich

Update: I first did a compression test tonight and was unable to heat the motor up first, however I had 107 psi on the top cylinder and ~100 psi on the bottom cylinder, so I took the carb off, replaced the cam follower roller, replaced the vacuum lines, and started to take apart the carb. Now I've fell into a pile of sh^%#$T, After removing the bowl drain plug and looking into the high speed orfice, I could tell someone had mangled it up trying to remove it or clean it. My problem is now it is unremovable. It look as if the bowl part number is 313355. Anyone know of a source for the bowl? I guess this could have been the problem, with the wet fouling if the orfice was enlarged, huh?<br /><br />Thanks in advance,<br /><br />DavidT

 

[alcan]

Re: 77' Johnson 25 cuts out, runs rich

Hi David<br />Good work! Well at least we know what the problem is. Now is the easy part, figuring out what to do about it. The OMC part # for your high speed orifice is 320921. They make a special tool (screw driver) for removing these orifices. If yours is so buggered up that you can't get a purchess on it, you are going to have to be a little creative. An idea might be to drill it out large enough for an easy out. I wouldn't look for another bowl just yet, unless it is plainly obvious yours is beyond repair. Keep us posted on the progress, mybe some of the other guys will have some ideas on this as well.

 

[DavidT]

Re: 77' Johnson 25 cuts out, runs rich

Called my local OMC dealer and he confirmed what I thought, the bowls are no longer being made. But, he stated that I could come down and rummage through and old salvage parts bin. So I go down and low and behold there are at least 10 similar carbs on the shelf, so I bought the one that most resembled my carb for $15.00 and bought a new high speed orfice, plus he removed the old one onsite. I've cleaned it up and it almost looks new. I hope to try to run the engine tonight.<br /><br />Thanks for the help,<br /><br />David Thomas

 

[alcan]

Re: 77' Johnson 25 cuts out, runs rich

Hi David<br />Wow, that guy took good care of you. It's always nice to hear about the good things that happen. I have never been a marine dealer myself, but business is business and I know first hand that if a customer thinks he got the shaft, they tell everybody. Give the same guy a screemin deal and he tells no one. I excited to hear the out come of your project. I hope this cures the whole problem.

 

[DavidT]

Re: 77' Johnson 25 cuts out, runs rich

Well, the only thing that came out of the whole ordeal is that the idle speed needle gets the motor running at 1-1/4 turns out whereas before the it required 4-1/2 turns out. The unit is still loads up, runs rich and fouls the plugs. My father inlaw said that he put new fuel in the tank 2 weeks ago, but tomorrow I'm going to get fresh 93 octane with the appropriate mixture of oil and try that. I also rechecked the compression after the motor idle for a minute or two and the two cylinders read 107 psi and 103 psi so I know thats not the problem. <br /><br />Once again any help is greatly appreciated.<br /><br />David Thomas

 

[DavidT]

Re: 77' Johnson 25 cuts out, runs rich

Last night I decided to pull the head of the boat and look at the head gasket and what the heck happens, broken head gasket bolt. Anyways, what does a blown head gasket look like. The metal rings are intact and I didn't really see any burn marks which may indicate leaking water or compression. The head had a light coating of oil, gas and carbon. The pistons where covered with carbon. I looked at the cylinder walls. The engine has definately been honed at least once. I saw some linear shiney marks up an down the cylinder walls but the compression was at 103psi and 107 psi. I don't think the head gasket was an issue but I checked it anyway. The CD2 ignition is coming under scrutiny again but there was a good spark over an 1/2 inch gap with a spark tester.<br /><br />Any comments greatly appreciated,<br /><br />David Thomas

 

[alcan]

Re: 77' Johnson 25 cuts out, runs rich

Hi David<br />As you noted your compression #s are fine. From your description the condition of your cylenders are ok. Snaped off only one head bolt. Thats pretty good for that vintage motor (usually worse). Ok, lets fix the head bolt and get on with repairing this puppy. There is no doubt that this motor has a fuel system problem. Lets recap, you have compression, you have spark to both plugs, the only thing left is fuel. When you istalled the new bowl and new high speed orifice, Did you also install a carb kit? I have this friend, he bought a used 1967 25hp johnson. Use it once, said it was no good. I took a look at for him, cleaned and adjusted the points and gave it a general going over. Provided him with a list of regular service parts to obtain so I could do a proper job for him at a later date. The motor runs like a swiss clock. He took it out, Wouldn't start, squeeze bulb no good. Took out again, no start. Brings it back to me, sure enough, no start. The plugs were wet. But they were wet with water not fuel. The carb bowl was full of water. I haven't had time to look in his 6 gal tank yet, but what do you think I'll find in it? This engine runs sweet on my shop tank. One thing you might check is the choke spring. Maybe your choke is sucking shut on you at higher RPMs. Of course you will have to remove the air silencer to check this. Your problem is too much fuel and not enough air. Now all we have to do is figure whats causing it. Keep us posted.

 

[DavidT]

Re: 77' Johnson 25 cuts out, runs rich

Update: While trying to remove the bolt I decided to run my finger inside the cylinders. Unfortunately the bottom cylinder feels like a ruffle potato chip with lots of scoring. I'm wondering if gas is being pushed past the rings or something. Do you think this is fatal with the heavy scoring of the cylinder walls.<br /><br />Thanks,<br /><br />David Thomas

 

[alcan]

Re: 77' Johnson 25 cuts out, runs rich

Hi David<br />As I am not there to see whats going on, it's hard to say. Your latest info is not good. As I see it you have to choices. Put the head back on it and remedy the fuel problem and run it the way it is. Or tear it down and over haul the power head. If in fact your compression test was accurate and the #s posted were correct, the engine should run. How ever, it's begining to sound like over haul time to me.