1996 Johnson 50 Not starting

[saltchuckmatt]

Carb, carb, carbs. When they don't idle correctly the carbs usually are to blame.

 

[janul15]

No success yet. Fresh fuel used. I tried putting a few drops of this into each combustion chamber, still the same; cranking but not firing. What could cause that?

 

[racerone]

It should bark and roar for a second or so.------So you have no spark.----Spark at the wrong time.----No compression.----Should not be hard to figure this out.

 

[janul15]

Compression is 150psi on both cylinders. Spark is good at 3/8", on both. New spark plugs, seen them sparking. So I must look at timing. The manual says the boat should be on the water for much of the timing check. But I need to get this to start and run a bit first. What timing adjustments can I make while the boat is dockside. (I'll look through previous threads on "timing" in this forum)

 

[janul15]

Timing result, on cranking the engine. The timing appears way off, firing at about 60deg ATDC. Linkages done to specification for my engine BJ50 BELEDS. Spark control rod is at 2.5". (For some other engine models, and for 4amp charging systems, this length should be 2 1/16"). I have, in the past , replaced the stator assembly and the timer base assembly. Could I have refitted them in the wrong position (only one way for the stator to go)? I can easily reduce the length of the spark control rod to 2 1/16", and let you know the timing test result again.

 

[racerone]

You are pushing the key in and holding it in while cranking it over for cold start ?

 

[janul15]

I'm not at that stage yet. I must sort the timing out and then inject a few drops of fuel directly into the chamber, to prove I can get a short term start. The timing stays way off (about 60 deg ATDC), regardless of the length of the spark control rod. The stator can only be fitted in one position. The flywheel is battered on the outside, but looks sound on the inside. Can the centre of the flywheel, which includes the groove for the flywheel key, have been moved out of position, after some impact ? I would attach a photo but it won't upload at the moment?

 

[racerone]

Magnets on hub may have shifted.---Post a picture of flywheel keyway and gap in magnet.

 

[janul15]

I hope these pictures show if something has moved.

 

[saltchuckmatt]

Will be interesting to see the reply on this one. It appears to me that your magnets are fine and I would think that would be a pretty rare thing but maybe that's older flywheels.

I'll be monitoring to see what the what the outcome of this is.

 

[racerone]

Use a pencil in sparkplug hole.------Mark TDC for each cylinder.------Now use timing light to see where each cylinder is firing.

 

[janul15]

Checked TDC for both cylinders with a pencil. Top cylinder is as marked on the flywheel. Bottom cylinder TDC is at 180 deg. to top cylinder TDC. Timing light shows sparking on both cylinders is about 30 deg. after TDC. I include a picture of the top of the flywheel, which shows the keyway position pointing at bottom cylinder TDC mark.

 

[Crosbyman]

backtrack... is this a new to you engine ?? did it ever run good ?

 

[janul15]

The engine is not new to me. It has run, but not consistently. Most of the few years I have had it, I have been trying to fix one issue or another. Recently, the problem is the non-start issue. Spark good, compression good, ruled out fuel issue by injecting pre-mixed fuel into the cylinders- still not firing up. I've found that the timing is seriously out, now I need to find out why.

 

[janul15]

I'm trying to work out why my timing is around 30deg or more, retarded. I have just read on another forum (MarineEngine.com) that someone found that an aftermarket trigger caused a similar fault on his Mercury. Is that what I know as the timer base? Mine was replaced some years ago, although I don't know if problems with my engine coincide with that replacement.

 

[Crosbyman]

any chance it was mounted off-set on the mounting holes ???

 

[racerone]

The trigger unit / timer base is not bolted down in place.-----Impossible to be installed wrong.

 

[ct1762@gmail.com]

the only thing that can make your timing that out of whack is a sheared flywheel key, or as racer said a slipped inner magnet for the sensor coil. a flywheel will shear it's key easily and quickly if it had sheared previously and the tapers were not lapped together again. what are the slow speed needles on the carbs set to? should be around 3.5 turns out i think. another thing with ignition: you can have spark (usually weak but not always easy to tell) at the plugs, but none when cranking (lower rpm than with plugs out). does it spark with plugs in? might have a weak or dragging starter if so...

 

[janul15]

Thanks for your replies. Racerone, I've now got the picture I think you needed. It shows the notch in the inner (ring) magnet in relation to the manufacturer's mark on the flywheel. Am I right to think they should line up.? If so, then my ring magnet has slipped. I can move it a bit by hand.

 

[ct1762@gmail.com]

Thanks for your replies. Racerone, I've now got the picture I think you needed. It shows the notch in the inner (ring) magnet in relation to the manufacturer's mark on the flywheel. Am I right to think they should line up.? If so, then my ring magnet has slipped. I can move it a bit by hand.

well if you can move it it slipped! found the issue. you can also see the glue is cracked. i dont think that white mark is a reliable way to re-set the magnet. i just grab another flywheel.