Outboard advice, please (fault)

[Mikefule]

Hi,

I have a Johnson J3BRESR, 2 stroke, 2 cylinder outboard. I bought it 2nd hand.

The outboard starts as well as any old 2 stroke will: a bit of choke, 2 or 3 pulls, and sometimes you need to restart it 2 or 3 times as you juggle the choke and throttle. Once it's up and running, it runs OK for a while.

The problem is that after a few minutes of running (it may be 10 minutes, it may be much longer) it starts to hesitate and sputter then it dies.

Secondary symptom: if it's running OK at low to medium revs, it bogs down if I open the throttle.

It seems worse under load: that is, when it's in gear, the bogging down is more noticeable than in neutral.

I have evidence that it has a new impeller, and there is a spray of water out of the holes. Good. (This is not an outboard with a single strong jet of cooling water. There are several holes low on the leg and the water sprays out in a mist.

I've put new plugs in, properly gapped. The old ones were a bit rusted and the white ceramic was discoloured.

I'm using fresh fuel properly mixed 50:1 with marine 2 stroke oil.

The main (high speed) jet is not adjustable. I have adjusted the low speed idle jet as directed in the manual, and that has smoothed it out.

There is no air filter to check/clean/replace.

I had the fuel filter out and cleaned it.

There is nothing in the manual about how to get to or adjust the points, but I have evidence that the previous owner had the points checked at a recent service. (Recent = undated, but it's a genuine document, not too faded, and I have good reason to trust the vendor although I don't know him personally.)

The only remaining thing I can think of is the carburettor may need cleaning. This is at the limit of my technical knowhow and there is nothing in the manual about how to remove it. I did that job once, 20 years ago, with an engineer friend.

After the outboard let me down yesterday, I spent some time on it this morning and thought I'd aced it. It was burbling away happily in the tub for 15 or 20 minutes, in or out of gear. Allowing for the need to be gradual with the throttle, I was able to run it fast or slow. Then suddenly it started the old hesitation, sputtering and died.

Any suggestions, please?

[Allye]

Sounds like ignition to me. Points are a simple thing to inspect, clean or replace. There are sparks and then there are sparks if you get me. Just because it’s giving a spark doesn’t mean it’s good enough.

[paintman]

I presume you're running it off the internal tank?
And the tank breather & any shut-offs, internal to external tank changeovers, hoses & filters inline between the tank are open AND not blocked/partially blocked?
I've seen cars & bikes where running fine for a short period then cutting out have been caused by blocked/partially blocked breathers & bits of breaking down fuel line lodging in the carb. Removing the filler cap allows air in & reveals the culprit if the breather is the issue.
Thread on pistonheads in the past couple of days where a blocked tank breather was the cause on a BMW 635csi, slackening the filler cap restored normal running. Be careful not to spill fuel if you try it.
And one from April with a ride-on mower where bits of rubber from the fuel line had partially blocked the fuel line from the tank reducing flow to a dribble.
I would suggest stripping & cleaning the carb. Resist any temptation to poke bits of wire into the jets.
Don't know if these might be of any help?https://www.boats.net/catalog/johnso...990/carburetor
https://blog.marineengine.com/2018/0...by-joe-reeves/

If you do decide to strip it then I'd suggest taking plenty of photos as you go so you can then look back at what it should look like. Makes life a lot simpler!

[Mikefule]

Thanks for the two replies.

I have now decided on discretion rather than valour and have taken it to Lincoln Marine Services, who have always been fair with me in the past.

I have tried running it with the fuel cap loose/off and it ain't that.

I might have been prepared to have a go at the carburettor However, getting at the points means digging deeper into the engine than my experience, skills and facilities would allow.

I'll see what LMS come up with.

Thanks again.

[slate1234]

got to be the coils when they get old they crack and causes the problem you seem to have

[Mikefule]

Originally Posted by slate1234

got to be the coils when they get old they crack and causes the problem you seem to have

Nope. I posted the outcome in a separate thread. Turns out the previous owner had put the wrong plugs in and I had foolishly bought new ones "replacing like with like". All sorted now.

[Nos4r2]

Pop the flywheel off (you'll need the correct puller) and have a look to see if the coils are cracked. Used to be a common issue with Johnrudes, they'd crack and fail when hot, cool down and work, then fail again ad nauseam.