8 hp johnson won't stay running

[Beek14]

I've got a 1990 8 hp Johnson outboard, and I doesn't want to stay running. It will start with one to two pulls, but every like 5-10 seconds it starts to try to die off, not wanting to stay running. I can even throw it in forward at full blast, and same thing, it will run great for a bit, then start to die off. So it's the same weather it's idling or going all out. It must be a fuel issue, but i'm wondering weather it could be a carb issue, or possibly a fuel pump? Let me know what you think. Thanks.

 

[Vic.S]

Re: 8 hp johnson won't stay running

Tank venting OK?

Try pumping the bulb. If that keeps it going then look at the fuel pump and the possibility of air ingress into the fuel line.

If choking it a little helps then look at the carb mixture adjustment (but its only got an idle mixture ajustment) or consider that the carb may need cleaning.

Needle valve/ float sticking perhaps and not opening.

Some other fuel starvation problem.

Always a smart idea to replace the plugs before tearing other things apart, and to check the sparks but agree it sounds like a fuel issue.

 

[bankerjohn]

Re: 8 hp johnson won't stay running

It must be a fuel issue, but i'm wondering weather it could be a carb issue, or possibly a fuel pump?

It could be either or both ... or it could even be the primer bulb on the fuel hose.

You didn't say if the motor is new to you, or if this was the first time it's been started in 2 years, or if it ran fine last week. A few more details of your circumstances would help!

 

[Beek14]

Re: 8 hp johnson won't stay running

Well that's because this is a hobby of mine, and the motor is actually one I'm fixing for a friend. It didn't run at all before I got to it. I changed the needle valve seat already, as that was sticking before and had a groove wore into the pin head. It's got new spark plugs in it, which are working properly. The primer bulb does go flat when it is running, which I have considered a problem as well, but I have switched lines and bulbs, but that one does the same thing too. I suppose they could both be getting bad since they are both older. But then again playing with the choke a little does seem to help too.

 

[film495]

Re: 8 hp johnson won't stay running

fuel pump

 

[CHRIS WOJCIK]

Re: 8 hp johnson won't stay running

Try Replaceing The O-rings On The Fuel Hose Connectors............make Sure The Primer Bulb Arrow Is Facing The Motor

 

[Vic.S]

Re: 8 hp johnson won't stay running

The primer bulb does go flat when it is running,

In which case it is not air ingress at the fuel connector or a bad fuel pump. It sounds more like a fuel flow restriction from the tank or the tank not venting, although I expect it to run for longer than the few seconds you mention.

If you can keep it running by playing with the choke a dirty carb is the prime suspect even if you think you have already cleaned it!

I fancy choked outlet from the tank ... causing the bulb to go flat , and dirt in the carb.

Have you looked in the tank to make sure its not full of muck.

 

[Beek14]

Re: 8 hp johnson won't stay running

Well there's no question that it isn't bad fuel in the tank. It's the same tank I use on my own every day motor with fresh fuel (hard plastic tank). It's not gummy at all, it runs my other motor great. Only difference is I have to switch lines because my every day motor is a mercury, which has a different fitting so I run an evinrude connector to the tank, and a mercury connector to my motor. But that is why I can't use my every day line for testing this one. I have tried playing with the choke a little bit thinking maybe it was getting better, I guess I could keep going at it. Also, yes the primer bulb is facing the motor, that's an easy one. It wouldn't be able to run if it wasn't.

 

[bustedmp]

Re: 8 hp johnson won't stay running

I am having pretty much the exact same problem with my 89 8hp. The major difference being when my dad and I pulled it out of storage and prepped it, it ran great for 20 to 30 minutes. It idled great, throttle response was very good under load, it idled for 5 minutes and when I gave it throttle it picked up very nicely. I towed it 26 miles to my house and now it will run for 10 or so seconds and then die. I replaced the plugs and checked spark. fuel is flowing to the fuel pump very well, new fuel, even a new tank. It will run some what with the starter enrichment knob pulled out, but it will not rev up, and within a few seconds of pushing the knob in itg dies no matter what position the throttle is in. It will not even try to start unless the primer is used, and even then I can not idle it down at all. I am thinking the long storage had caused some build up of junk in the carb and that towing it caused it to block something in the carb.

I am going to pull the carb and see if I can find anything, I will post back when I get it figured out. Till then, I am going to keep an eye out here for a possible solution.

P.S. What is the base setting for the low speed needle?

 

[bustedmp]

8hp johnson fixed!!!!!!!!!!

8hp johnson fixed!!!!!!!!!!

I found the culprit of the running problem. In the fuel bowl on the carb,the tube that feeds fuel to the upper section of the carb had badly deteriorated and must have got shaken off during the trip home. Well since I work on atv's I had some small fuel tubing on hand, and put a new section in the carb, and now it runs great.

 

[agaurolex]

Re: 8hp johnson fixed!!!!!!!!!!

Re: 8hp johnson fixed!!!!!!!!!!

I found the culprit of the running problem. In the fuel bowl on the carb,the tube that feeds fuel to the upper section of the carb had badly deteriorated and must have got shaken off during the trip home. Well since I work on atv's I had some small fuel tubing on hand, and put a new section in the carb, and now it runs great.

I am having the same exact problem with my 8hp 85 Johnson. I had the carb apart to clean do not recall see the tubing that you described. Does this tube run on the outside of the carb or is internally?

 

[Vic.S]

Re: 8 hp johnson won't stay running

The tube referred to I guess is #26 in THIS DIAGRAM

Does not exist in the 1985 model

See TD's "Top Secret File" at the top of the board index for a link to the instructions for setting carb needles.

 

[bustedmp]

Re: 8 hp johnson won't stay running

Yeap, that is the tube I am refering to.

 

[agaurolex]

Re: 8hp johnson fixed!!!!!!!!!!

Re: 8hp johnson fixed!!!!!!!!!!

I am having the same exact problem with my 8hp 85 Johnson. I had the carb apart to clean do not recall see the tubing that you described. Does this tube run on the outside of the carb or is internally?

A second teardown of the carb with more focus on cleaning the upper section seems to have resolve the "dying at idle problem". I also checked the fuel pump at idle by yanking out the output line and fuel appeared to coming out. So that directed me back to focus on the carb. Don't recommend the kids trying this at home. Also splurged on a new tank and fuel since I saw rust sendiment in the tank. All of this was probably contributing factors.

Thanks all for your help......will see on the water!