2003 johnson 150 hp troubles. still can't get this thing to run right.

[4.0l sahara]

Okay so we have a fourwinns with a 03 150hp on it. It hasnt run right since it was brand new. This thing has me stumped. Ive posted a few times on here trying to figure it out. It has gotton worse the last 2 years and im getting sick of this thing. The problem is it runs like crap just off of idle and after running around for a while it can be really hard to get it going again. When it does start you have to feather the throttle to get it to rev up then it clears out and is fine. It runs great up top. I've rebuilt the carbs and set the float hights. And checked the whole fuel system over more than once. Tried a few sets of plugs for the hell of it. Checked spark,compresion all that stuff. Poured over the thing top to bottom. It has very low hours on it too. I would love to be able to just take this pos out and just have fun and not worry about getting stuck or any crap like that.:facepalm:

 

[oldcatamount]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

Let me start by saying that I know nothing about your motor and I don't want you to run out and buy parts on my say so. Having said that, it sounds (to me) like you have 2 or 3 cylinders that are sucking air instead of fuel. There are a dozen o-rings on the fuel manifolds that need to be in good condition and tight. I would suggest (if you haven't already done this) to check all the bolts/screws on the fuel manifolds and the carbs to. I doubt there is an adjustment on the carbs but, if there is, it's very important that all carbs open exactly at the same time. Wish I could be of more help to you but a 2003 motor is brand new to me and I have zero experiance with them.

 

[4.0l sahara]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

Yes there are a ton of o rings. One other thing is the stupid plastic float bowls on the carbs are prety warped. a few are a little damp around the gasket from being warped. Does anybody make aluminum float bowls for these?

 

[oldcatamount]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

I believe that you can take off the warped float bowl, turn it upside down and sand it (lightly) on a flat surface with fine sandpaper. That would take the warp out of it. Just be sure to clean out the sanded material before re-installing. I really doubt that the float bowls are causing your problem though. Since you say the problem is getting worse, leads me to think that the carbs (at least 2 of them) might be still crapped up with something or, are not in synch with the others. Can you do a "link and synch" adjustment on your motor?

 

[4.0l sahara]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

yes the carb butterflys are all in sync. Ive checked the timming a few years ago but never tried totally doing a link and sync. But I really don't think it's timing related.

 

[Faztbullet]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

Warped bowls and air leaks around idle passage plugs on throttle bodys make em run like crap....

 

[jonesg]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

The carb bowls warp if the screws are over-tightened, so go easy on them.

"When it does start you have to feather the throttle to get it to rev up then it clears out and is fine. It runs great up top. "

If this describes the problem , I'd say its loading up (rich) at idle or idle timing is wrong.
Check the choke solenoid for a leaking end cap.
Check idle pickup roller for the clear plastic sleeve, they break and throw idle timing off.

You didn't state the compression numbers or how you tested for spark.

 

[4.0l sahara]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

What are the idle passage plugs?

 

[4.0l sahara]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

Okay so the plann is to pull carbs back off and replace all the bowls and check float hight and neadle and seat again. So my only choice is the plastic bowls I think?

-pull manifolds off and check the reeds and replace all the throttle body o rings this time. The big molded ones.
-recheck compressio
-Check primmer solinoid

 

[Big flop]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

Sorry if I missed this already answered.
When running at the problem RPM does bumping
choke help?
Have you adjusted idle mixture screws?

 

[4.0l sahara]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

Never tried the primer. Also I've played with the idle screws. They don't help at all really. They do change how it runs but not any better.

 

[boobie]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

Dumb question time. What temperature is it running at at idle? Is quick start working properly? What spark plugs do you have in it?

 

[Big flop]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

Check the air jet size that's in the front of
the carb. Make sure they are right.
Use on line parts catalog with model #.
some of them show a new part number
for 2003 for the jet.

 

[4.0l sahara]

Re: 2003 johnson 150 hp troubles. still can't get this thing to run right.

Dumb question time. What temperature is it running at at idle? Is quick start working properly? What spark plugs do you have in it?

It warms all the way up to 175 i think. Also the quick start works the way it should. It has new t stats.