Rough running Johnson

peteandthira

peteandthira

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I have a 3.5HP Johnson 2-stroke outboard, which has been 100% reliable so far but never seems to be "on song". At or above about half throttle it seems to take about 5 mins before it really gets going and sounding nice. Prior to that it seems to be a little unsteady, as if making up its mind.

My suspicion is that it is running a little rich, but I can't find any means of adjustment on the carb. It is well serviced and recently had a new plug which made no difference.

Does anyone have any knowledge of this sort of thing?

Regards

Pops
 
My Johnson 9.5 also performed in a similar fashion. Constant changing engine note, at any minute you expect it to cut out. At times it did cut out, only to restart without trouble. Had the engine serviced and faulty HT leads were found and replaced and since then...no more problems.
 
fuel side of things

check the floats ok also needle valve not iffy last check the fuel is getting through ok as a blockage could cause problems under load
electrical
as already said leads
then coil
then check its advancing
cheers
Mick
 
What year and /or model number?

I think tho' the 3.5 was only made from 2001 to 2006. If it is one of those then the mixture is fixed.

If it really is running rich the check that the choke is opening properly and that that it is not flooding slightly due to the needle vavle not seating properly.

The alternative is that it is running weak and that the carb needs cleaning.

You are using fresh, clean fuel I hope.

The plug is correctly gapped?

As suggested check the HT lead. and other electrical connections
 
Go to the parts diagrams on the BRP website and enter your engine details and you will be able to get a diagram of the carb

I think you must be refering to the idle speed adjustment screw #21

You've seen my edited post above?

A very good place to get advice on outboards is the iBoats forums Where you will find separate boards for different makes. Quote the full model details though.
 
VicS

Thanks again, just seen your edited version. Unfortunately the web link throws up a long-winded error code so I haven't been able to see what you intended.

Idle screw eh? Well since I'm sitting on the boat now I might get it going and see what I can find out!

Thanks again

Pops
 
The link works for me OK. Try it again.

If not try this one http://epc.brp.com/default.aspx?brands=ej&lang=E but it is the same.

You have to close your favorites list to see all of the first screen (That's wierd) but then it should all work OK.
You'll find the parts diagrams quite useful.

Also check that you have an uninterupted fuel flow to the carb. There is a filter in the tank outlet. Also that the tank vent, in the cap, is opening properly and is not obstructed.
 
VicS

Thank you for your continued interest! I still can't get to that link for some reason. It throws up a page with this on it:

There was an error processing the request: System.NullReferenceException: Object reference not set to an instance of an object. at _Default.CreateSession(String Brands, String Language) at _Default.Page_Load(Object sender, EventArgs e)

Errr.... maybe I have a problem with more than just my outboard!

I am going to strip it down on the next rainy day, take the carb out, which looks really simple, and check it all over. I have already checked the fuel flow, which runs out in a continuous stream from the bottom of the carb when I undo the little screw there. The filter is fine, the fuel is clean and the vent hole in the filler cap is clear.

If it doesn't run better after that, maybe I can PM you for advice if you don't mind!

Best wishes

Pops
 
Re: fuel side of things

This is the url of the carb diagram but the website has diagrams of all the other sections as well

http://epc.brp.com/Scripts/ImgServ.exe/c...IF=G&ilRE=8

Ad this is the list of the carb parts.

http://epc.brp.com/scripts/EmpartISAPI.d...amp;assem=59965

You could try getting at the website from

http://www.evinrude.com/en-US/ then click on "parts and accessories" and then on "engine diagrams"

If checking out all the fuel system does not solve things then its the ignition system but beyond the plug, the lead and the other electrical connectons about the only way to check out the electronics and the coil is to get a dealer to look into it.

Not a silly fault with the stop button I suppose
 
Re: fuel side of things

VicS

I don't believe there is a stop button problem, the engine never actually cuts out - it just seems to want to make the decision to increase power for itself, after a short deliberation! When at high power it eventually smooths out, but it takes a few minutes to stop doubting itself. It seems that it may be running a little cold and then warms up later.

I can't explain it any better than that. It is going to get a thorough looking at, as soon as SWMBO will give up the galley surfaces. I got your carb diagram, thank you for that.

Thanks for your perseverance Vic.

Pops
 
Re: fuel side of things

[ QUOTE ]
I don't believe there is a stop button problem

[/ QUOTE ] No nor do I really. I was just trying to cover all the possibilities no matter how unlikely.

I would seriously consider that the carb needs cleaning but it really should not in only 3years unless youve got some water in there at sometime or have used some mucky fuel or very old oil in the mix.
 
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