1987 15HP Johnson problems:

[Mullerhawk]

Hi,

I purchased a cheap boat yesterday with a Belgian made Johnsson 1987 15HP (BJ15BACUD) manual pull engine attached to it.

When starting the engine I have problems keeping it in idle even though I have pumped up fuel pressure propperly. It tends to die on me unless I quickly put it in gear and gives it some gas. I have tried to adjust the idle screw and also turning the idle speed adjuster on the throttle handle without success.

When running the engine it seems to work fine. But hitting about 90% throttle it stutters a bit and runs a bit uneven (even drops some speed). Keeping 90% throttle it runs even and perfect.

From reading some guides it seems maby to do something with a dirty carb, or even some problems with the reeds not opening/closing properly ?!

The engine was fitted with NGK B7HS plugs. And from reading BR7HS or even BR6HS is recommended - can it affect the engine?! I have not yet looked at the color and state of the plugs yes. But will do that tonight. The fuel tank was also fitted with a rather long hose - around 3 meters.

What is your recommendation? Does it seem like a carb problem? Or is there some other apperant problem that comes to mind?

I appreciate your input.

// Michael

 

[raczekp1]

Re: 1987 15HP Johnson problems:

the best info you can get is to read this articles
http://www.sschapterpsa.com/ramblings/Ramblings.html
at the botom of page.
its very good motor, i'm looking for this model in Sweden(tradera, blocket)

 

[BonairII]

Re: 1987 15HP Johnson problems:

Does the manufacturer actually recommend NGK by name? Normally I read that NGKs don't perform as well as Champion etc.

A carb rebuild is normally the first thing that is recommended as well. Could have crud in your low speed circuit causing the idling probs. I don't know what would be causing the WOT issues.

 

[Jim311]

Re: 1987 15HP Johnson problems:

NGK is what they sell at the local 'Rude dealer. A friend of mine told me once that it was common to have problems with your low speed/idle jets on your carb because the bores of them are smaller and more easily clogged, so it may run fine wide open if you can get it there, but not idle worth a damn. You could have other problems too, but a carb clean seems to a lot of idle problems that people around here post. Often times they complicate things too much before trying a carb job. You could try running some SeaFoam or other fuel additives as well.

 

[Mullerhawk]

Re: 1987 15HP Johnson problems:

Thanks for your help,

I dismantled the carb yesterday - and it's the newer model type with the black plastic lid. I could not see any apparent problems in the carb. The float was made of plastic and not the old cork variant. The bottom of the float lid was clean and no apparent traces of water or contamination. But what puzzled me was that only 5 of the 7 screws was mounted on the top lid (the two longer ones was missing). Strangely enogh looking at the pictures at http://www.sschapterpsa.com/ramblings/Johnson_9.9_carb-fuel_pump.htm it's missing the same two screws?! But then I also found what might be the culpritt, the black lid have a elongated hairline crack running along the idle screw.

I checked what a new lid cost - and it's a staggering $75 for a piece of plastic. I have now mixed steel epoxy and covered the cracked parts, I have also ordered a carb renovation kit to make sure that all the parts Is brand spanking new when re-attached.

Since I don't have a manual. What's the article number for the recommended champion plugs? And is there really any apparent difference between them and the NGK brands?

 

[Mullerhawk]

Re: 1987 15HP Johnson problems:

Problems solved,

I put the carb back together yesterday. When I twisted the throttle I could see my exoxy cracking. The black lid was lifted a bit by the force exerted by the CAM unit. So I had to remove the carb again, drill and tap a new hole just infront of the cam unit. Assemble everything back together again and put new expoxy as an extra safety messure . What also came to mind was with the cracked black lid the cam unit actually turned the throttle butterfly more than 100% open - it can open a bit more without stopping. Thus when running before it probably opened like 110% and inverting the butterfly a small bit making the engine run uneven at 100% throttle.

Testdrive:

I twisted the idle screw out 4 turns as recommended by the above link. Tried to start the engine. The engine stuttered a couple of times, but no go. I then tried only 1 1/2 turn - viol?! The engine started right away - almost perfect idle. I fine adjusted a bit and put the idle knob back. Tried cold start, warm start. One pull! Thats all I need now.

Went for a testride. Started on 1/2a pull. Accellerated perfectly up to 18knots without any hesitation. Ran the engine for half an hour. Killed the engine, started again within 1 pull. Engine is like new again

Thanks for your help, this forum is invaluable!

// Michael

 

[Rick.]

Re: 1987 15HP Johnson problems:

Congratulations on a job well done. I hope she runs fine for you for many years. Best of luck. Rick.

 

[BonairII]

Re: 1987 15HP Johnson problems:

Congrats! Nice to see people have success. Tons of "I'm at my wit's end" threads....nice to see the victories.

 

[Mullerhawk]

Re: 1987 15HP Johnson problems:

Thanks - appreciate it

Now for my next fix: Convert the "AC lightning" outlet with a 3-phase rectifier -> 12v outlet to power a charger!