1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

Have a 140HP Johnson that for whatever reason will not go anywhere (above 2400RPM). Here is a video of the motor revving underload if it helps?

http://www.youtube.com/watch?v=n_LCy8wBs9I

Starts instantly and idles like a brand new motor.....

Here are the steps I have taken so far:
1) Replaced fuel tank.
2) Replaced fuel hose to tank.
3) Replaced fuel filter on pump.
4) Replaced every internal fuel line.
5) Rebuilt carbs completely.

Tests/troubleshooting:
1) Passes 7/16" gap spark test with nice blue spark on all holes.
2) Passes compression test 130-115
3) Passes pumping primer bulb with throttle applied (no change in performance)
4) Carb butterflies FULLY open at WOT, verified.

I am at wits end with this motor. I really need help. The lever on the control box that advances the timing does allow the motor to rev really high (above 2400 RPM CAP, in neutral). Prior to rebuilding the carbs, and fuel filter, the motor would only hit 1900RPM. On the low end, it seems great. Once you get to 40% and up it sounds as if the motor is falling flat on its face. Is there a timing advance that should be automatically going as it throttles up, because it almost seems like that might be the problem. It sounds great down low, but gets held back with 40% or more throttle.

My offer stands, if you tell me the problem and the proper steps to verify its the problem (ie, step by step troubleshoot). I will paypal you $10 the day my motor goes true WOT...lol

Here is a link to my original thread:
http://forums.iboats.com/showthread.php?t=266497

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

Is the ignition stator plate going to full advance?

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

Will double check but I believe so.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

I don't think it is running on all 4 cylinders. Remove and ground one spark plug wire at a time, noting the change in performance each time. Whichever one (s) doesn't make any difference is the cylinder (s) that is not doing anything.

When you rebuilt the carburetors, did you remove and inspect the high speed jet orfices?

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

F_R said:

I don't think it is running on all 4 cylinders. Remove and ground one spark plug wire at a time, noting the change in performance each time. Whichever one (s) doesn't make any difference is the cylinder (s) that is not doing anything.

When you rebuilt the carburetors, did you remove and inspect the high speed jet orfices?

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Thats a great idea with the cylinder wire test and I will try that. All the cylinders feel like there getting up to temp and the plugs are warm. When I rebuilt the carbs, i removed the jets and blasted the crap out of them with compressed air, and 2 cans of carb spary. Carbs were really clean and had no varnishing or any dirt/grime.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

High speed jets (make sure you take them out). Make sure the three little holes in the carb thoat are not stopped up. The timing advance should move forward fully before the carbs move all the way. (link and sinc) How many sets of jets did you pull out?

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

2 low speed on the carb base and 2 high speed from the cover, for each carb. One at a time so they did not get accidently swapped. I had to grind down a screwdriver to fit it in the high speed orfaces. I also blasted ALL holes in the carb throats with cleaner and air. This problem came on INSTANTLY when the motor was running great, so I am not at all convinced its carb related.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

In the video it doesn't 'sound' like its firing on all cylinders under load, theres an oscillation to the sound.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

fouled plug? try pulling the plugs out and take a look immediately after running it wot.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

cdoliver said:

fouled plug

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Plugs are all brand new after I rebuilt the carbs. Checked them 10+ times today, none are fouled.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

jonesg said:

In the video it doesn't 'sound' like its firing on all cylinders under load, theres an oscillation to the sound.

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Agreed, it doesnt sound right to me either. All cylinders have good spark at idle, so I guess I have to try pulling one (and grounding) at a time and running it. If I still reach 2400RPM, then I know thats the cylinder thats not firing.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

You could do that same test at idle. You can confirm if there is a wet plug. What happens when you choke it at wot?

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

Something's broken. Pay up sucker!

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

It's definitely not firing on all four cylinders. I would check for a bad coil breaking down under load.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

shawn_nj said:

2 low speed on the carb base and 2 high speed from the cover, for each carb. One at a time so they did not get accidently swapped. I had to grind down a screwdriver to fit it in the high speed orfaces. I also blasted ALL holes in the carb throats with cleaner and air. This problem came on INSTANTLY when the motor was running great, so I am not at all convinced its carb related.

Click to expand...

The high speed jets are in the very bottom of the float bowl. Is that what you are calling the "cover"?

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

You can "see" a firing problem more easily by using a inductive timing light while running through the operating range.

You need to watch the timing advance as the control arm is moved forward. It should move just as it does with the warm up lever.

Be sure that the idle air bleed restrictors are in place in the carburetors

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

F_R said:

The high speed jets are in the very bottom of the float bowl. Is that what you are calling the "cover"?

Click to expand...

Yes, sorry. I am VERY new to outboard motors/terminology.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

ezeke said:

You can "see" a firing problem more easily by using a inductive timing light while running through the operating range.

You need to watch the timing advance as the control arm is moved forward. It should move just as it does with the warm up lever.

Be sure that the idle air bleed restrictors are in place in the carburetors

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1) Uggg. I guess I will add an inductive timing light to my tool kit....lol. Correct me if I'm wrong. You can just clip it ontop of the plug wire and it will stop flashing if the plugwire/coil stops firing? In the mean time, I have a PET tach that clips on top of the plug wires. I will try to see if that looses its sampling while reving the motor through the powerband.
2) I am 99% sure the timing advance arm was moving just as the warm-up lever does, but I will verify to be 100% sure.
3) Not sure what idle air bleed restrictors are, I will do some research.

Troubleshooting is made more difficult because the boat is moored and I have to do this all on the water....LOL

Thanks guys this is great stuff.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

In your video I could not see your linkage move. Did you notice if the linkage continued to move after it reached WOT? I am looking for an less complicated thought. Watch your linkage as you slowly increase throttle. See where it hits your WOT and then decide how much future it will go. I am thinking throttle linkage may not push linkage far enough.

Re: 1978 140HP Johnson, still wont go anywhere! $10 to whoever figures it out!!!!!

MikDee said:

It's definitely not firing on all four cylinders. I would check for a bad coil breaking down under load.

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Yup! Or the timing advance is badly restricted