2003 Johnson 150 idle rough?

[fishcrazy101]

This new to me boat has a rough idle and will stall on throttle up if not done abruptly. The WOT running could not be better though. I have replaced the fuel line from the tank to the motor with new and installed a filter/water separator while in the process. That seemed to help but did not cure the problem. I am a bit confused as to what I should do next. I have done a lot of reading in various forums and heard many people say that they rebuilt the carbs and that did not help this same problem. I have read others say that the seafoam treatment from a gallon tank with a bottle of foam and enough gas and oil to make up a gallon and run that through at idle in 10 minute intervals and rest for 15 min and repeat 2 more times and then hook back up to tank and run WOT for a while to clean the carbs will help. Others say that will not fix the carbs. I saw one post that said the low idle should be adjusted and that would fix the problem. I guess I could fiddle with that a 8th of a trurn as suggested and see if that helps. Should I do one carb at the time or all an 8th of a turn and see what happens? Or should I crank them all in to seat and back them out 34 turns and start fine tuning from there? This is a 150 Johnson Model J150PLSTM. Should I do a link and sink before I do the low end idle adjustment or do it after. I have no problem doing the rebuild on the carbs but dont want to do that if it isnt necessary. Since the motor runs so perfect at WOT I want to think that the link and sink is ok and the low speed adjustment is the think to try.

What would you do?

 

[fishcrazy101]

Re: 2003 Johnson 150 idle rough?

I really could use some advice on this. Anyone?

 

[fishcrazy101]

Re: 2003 Johnson 150 idle rough?

Please any help would be greatly appreciated!!!

 

[fishcrazy101]

Re: 2003 Johnson 150 idle rough?

Just need some seasoned advice here. I spent some time inspecting the motor and carbs last evening and looking at the throttle and just what actions on the motor were triggered bu moving the throttle leaver from neutral to WOT position. I noticed that nothing happened at all untill i got half way through the total travel at which time the spark cam roller was just beginning to move toward the Detent plate. It was not already touching the plate but some distance from the plate when the throttle leaver had begun its travel. So for some distance of travel in the throttle leaver the spark cam roller was not in contact with the Detant plate but moving toward it and therefore not activating anything. Is that right? Or should the spark cam roller always be in contact with the Detane plate? I wonder if a link and sync is indicated? Or am I just way off base here. I know that it says a special tool is required to perform this operation and the tool cost about $300.00 so I probably would just take it to a dealer that could do it. I feel that there is a lot of travel in the throttle leaver that is not doing anything at all till the spark cam roller starts actuating movement in the Detant plate. Sooooo ... Any insights here would be greatly appreciated.

 

[Haffiman]

Re: 2003 Johnson 150 idle rough?

The only link&synch needed on that engine is to be sure all throttle plates are completely closed when roller is off the cam.
At idle it should be a gap of min 1mm between roller and cam.
Idle rpm is then adjusted using the 'Low' tab on the bracket for the optical analyzer.
If your main problem is rough running all over the rpm range, I would suspect a fuel related problem.
Might be the vapor pump.
Might be a leak in the filter going into the vapor chamber.
Might be wrongly adjusted carb mix screws. (in throttle plates)
I would suggest to get an OEM manual first before you start adjusting the mix screws.

 

[Faztbullet]

Re: 2003 Johnson 150 idle rough?

Here is link(with pic's) to setting the pickup as it will slip over time/usage. Rough idle can be caused byirty carbs, flooding carb/s, improperly adjusted mixture screws,engine too cold(stuck t-stats) and staying in quickstart...
http://www.bbcboards.net/zerothread?id=357667

 

[fishcrazy101]

Re: 2003 Johnson 150 idle rough?

Haffiman Thanks for the info. The problem is rough idle to the extent of stalling out sometimes. The motor is perfect once you ger it moving and accelerating. Its just that moment before it takes off that is rough to get past. Sometomes you just have to slam the throttle to practically WOT to get it going. If you throttle up slow it will most of the time cut off.

 

[fishcrazy101]

Re: 2003 Johnson 150 idle rough?

Faztbullet Thanks for that link!!! I think you have made my day! Mytiming roller looks just like the first picture and requires quite a long travel of the throttle leaver to just get the roller in contact with the arm. Dont know if that will fix the idleing rough problem but may just keep me from stalling on throttle up. Thanks again.