At My Wits End!!!

[minkota]

Hello All, New Here and have a problem.

I have a 1988 120hp Johnson and it runs very rough (when it does run).

Things I have tried:


1) Rebuilt Carbs
2) Changed Fuel Lines
3) Changed Power Pack
4) Changed Coils
5) Chnged Stator
6) Changed Timer Base
7) Checked Compression (100+ on all Cylinders)
8) Chnged head Gasket Just because I had an extra Set
9) Connected an External Fuel Tank to Eliminate on Board Fuel System as a Problem.
10) Check Reeds, all appeared to be ok and functioning properly. I did not remove them I only looked at them when I had the carbs off

I am not a marine mechanic by any streach of the imagination, but I am a retired auto mechanic so I am familiar with motors. with that said I have exhausted every thing I know to check or replace on this motor, what else can cause a rough running motor or keep it from starting.

I have searched the forums but have not found any threads with similar symptoms. I just dont know what else to look at...Thanks in advance for any help.

 

[Rscardina]

Re: At My Wits End!!!

Have you checked timing? Have you looked at the carb butterflies to ensure eveything is in sync?

As you already know...compression, fuel and spark makes eveything go.

Whats the symptoms you are having?. VRO or not?.. Primer solenoid?

 

[wilde1j]

Re: At My Wits End!!!

You need to start logically and systematically diagnosing, rather than replacing parts as a first cut, or you will end up with a mostly new motor, maybe not running any better. Have you checked the timing and done a link and sync? What is max RPM now? Has choke/primer operation been checked? Do you have an OEM shop manual?

 

[minkota]

Re: At My Wits End!!!

Have you checked the timing and done a link and sync?

There does not seem to be a timing adjustment on it, and I have done a link and Sync.

What is max RPM now?

Motor does not run long enough to get a max rpm, it barley idles. Most of the time it will not even try to start.

Has choke/primer operation been checked?

Yes it is functioning properly.

Do you have an OEM shop manual?

Yes, I have a Manual.

 

[Rscardina]

Re: At My Wits End!!!

There does not seem to be a timing adjustment on it, and I have done a link and Sync.




Motor does not run long enough to get a max rpm, it barley idles. Most of the time it will not even try to start.




Yes it is functioning properly.





Yes, I have a Manual.

there is a timing adjustment..its under the flywheel..looks like a crew with a rubber base on one end. When you addvance the throttle it moves the timer base and it stopps on that screw with the black boot on it.

if you have a timing light, put it on cyl 1 and flash the light on the flywheel..see where its sparking. the other thing you can do is set WOT timing -4 degrees of what your engine calls for using the joe reeves method.. search posts for joe reeves method.. it will tell you how to set it on dry land without having to run the engine.. this method allows for WOT with a -4 dgree offset to what your negine calls for. mine calls for 18 BTDC..so for me I set it to 14..

that will get you super close to where you need to be and the bottom end will fall in line.

 

[Rscardina]

Re: At My Wits End!!!

"NOTE: If your engine has the "Fast Start" feature", you must disconnect/eliminate that feature in order to use the following method. The "Fast Start" automatically advances the spark electronically when the engine first starts, dropping it to normal when the engine reaches a certain temperature.

The full spark advance can be adjusted without have the engine running at near full throttle as follows.

To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary).

Rig a spark tester and have the gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4? less than what the engine calls for.

I don't know the full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28?, set the timing at 24?. The reasoning for the 4? difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4?.

If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4? which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place.

No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting.

Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes."

 

[minkota]

Re: At My Wits End!!!

if you have a timing light, put it on cyl 1 and flash the light on the flywheel..see where its sparking.

will this work when i use the starter to turn the motor, like I said it seldom starts.

"NOTE: you must disconnect/eliminate that feature in order to use the following method.

How Do I Disconnect the Fast Start, I see nothing im my manual about how to disconnect it.

 

[Rscardina]

Re: At My Wits End!!!

yes.. the idea is to have all the plugs out and grounded..so the motor should turn pretty fast. having a second hand is good so you can check spark while someone turns the key..

your more concerned about where the spark timing is rather than running it.. this will ensure your spark is hitting at the right spot and the you can remove that from the equation..

check compression on all cylinders while you are at it..they should read 100-130 on each, but more importantly you dont want more than 10% or so difference bewteen any clyniders.

put your plugs back in and conncet the wires...

after that, you are on to fuel..you can spray mix into the carb throats to see if cylinders pick up and get better..if so,, then you know its fuel delivery (you probably know this already)...

make sure you prime the bulb, turn the key and push in to cold start, then turn all the way and it should go..might take a few tries but if all checks out it should fire. once its going someowhat try squeezing the primer bulb..if she keepos running then your fuel pump may be problematic..

in short, start checking things off piece by piece and you will find it..

 

[Rscardina]

Re: At My Wits End!!!

will this work when i use the starter to turn the motor, like I said it seldom starts.



How Do I Disconnect the Fast Start, I see nothing im my manual about how to disconnect it.

your engine may not have this feature..i think 89 and after had this but your manual tell you if you have it....

its not about starting..its about turning fast enough to let the magneto do what it does to create power to generate spark..not concerned about it running at all yet..merely a test of spark

 

[boobie]

Re: At My Wits End!!!

Now I know this is a dumb question, but is the center magnet in the flywheel slipped or is loose ? Those old loopers were great for that.

 

[Sixmark]

Re: At My Wits End!!!

You may have to research it further, my 84 is equipped with "faststart" which shocked the hell out of me.

 

[minkota]

Re: At My Wits End!!!

your engine may not have this feature..i think 89 and after had this but your manual tell you if you have it....

I am pretty sure it has this feature, but nothing in the manual explains how to disable it. It only mentions the fact that it is there.

Now I know this is a dumb question, but is the center magnet in the flywheel slipped or is loose ? Those old loopers were great for that.

I do not see a center magnet, only the magnets that are cast into the flywheel, which appear fine.

 

[Sixmark]

Re: At My Wits End!!!

Here Ya go!!

To disable QuikStart, you disconnect the black w/white striped wire and ground the powerpack end of the wire to the engine block.

I found this here on the site for ya. You can thank Ezeke for posting it.

 

[minkota]

Re: At My Wits End!!!

You can thank Ezeke for posting it.

Thank You!!

 

[minkota]

Re: At My Wits End!!!

I forgot to mention this in my origonal post, when I try to start the motor (when it does start) it revs high and stays reved for like 3 seconds (which I assume is the quick start feature) and then shuts off and will not restart. although while it is running it is running very poorly.

 

[Pokertrampp]

Re: At My Wits End!!!

I had a similar problem and it turned out to be the head gaskets, but you said you already changed them. did you recheck the compression afterwards?

 

[nymack66]

Re: At My Wits End!!!

Check your wires from your power pack to your coils, Standing on the ground with the engine in front of you port =left starboard=right
Verify each wire from pak to coils ..
Cyl=2 Red&Purple Cyl=1 Blue & Red
Cyl=4 Red&Orange Cyl=4 Green &Red
Also unplug the connectors from the trigger and stator, look at each pin verify none is bent or off to the side, lube with an electrical lubricant re-connect and test ..

 

[Faztbullet]

Re: At My Wits End!!!

Doubt its the flywheel magnets as it has the 9 amp stator unless a 35 amp kit has been installed.

 

[mamm7215]

Re: At My Wits End!!!

Are the butterflies closing all the way in neutral? I just had this problem on my '81 90hp. Did the link n sync and everything but still cough/miss at idle. For some reason I thought to push on the upper then lower carb butterflies. The lower one did the trick, suddenly idle evened out never missed a beat. I'm sure my throttle valves are loose/worn but to "fix" I got a generic throttle return spring and hooked it to the upper sync plate and timing pointer base. Now it shuts tight and idles fine. This adjustment was done with cables and sync adjustments loose so no maladjustment could have been affecting the idle. Just a thought...

 

[minkota]

Re: At My Wits End!!!

Check your wires from your power pack to your coils, Standing on the ground with the engine in front of you port =left starboard=right
Verify each wire from pak to coils ..
Cyl=2 Red&Purple Cyl=1 Blue & Red
Cyl=4 Red&Orange Cyl=4 Green &Red
Also unplug the connectors from the trigger and stator, look at each pin verify none is bent or off to the side, lube with an electrical lubricant re-connect and test ..

I have done this several times to make sure it wasnt crossed or something. Thanks

Are the butterflies closing all the way in neutral? I just had this problem on my '81 90hp. Did the link n sync and everything but still cough/miss at idle. For some reason I thought to push on the upper then lower carb butterflies. The lower one did the trick, suddenly idle evened out never missed a beat. I'm sure my throttle valves are loose/worn but to "fix" I got a generic throttle return spring and hooked it to the upper sync plate and timing pointer base. Now it shuts tight and idles fine. This adjustment was done with cables and sync adjustments loose so no maladjustment could have been affecting the idle. Just a thought...

I will try that, maybe I will get lucky. I know I sure am tired of getting no change at all no matter what I do. Thanks