1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

[stumpknocking]

I have a 1983 Johnson 75 hp outboard Modle #J75TLCTE on a 2008 17' center console RockPort.
Had the rig for a year and she ran perfect. Next to last trip out she started sputtering and missing and finally died 20 yards from the ramp. Thought I had run her out of gas. 13 gallons of fresh fuel and the next time out she barely started.
Got her running and she was still missing and sputtering. Finally just used her to idle around. Steadily got worse and limped back to ramp. Good news is we busted 5 carp with the bow headed back.

The fuel primer bulb stayed hard the entire time. Tried to force feed her when she was coughing and the bulb was still hard.

Pulled carbs and cleaned them. They were spotless to begin with. Changed the plugs and checked the spark ( looked strong ) before installing them.


Could this be electrical? Just assumed it was fuel related with the symptoms caused by running a 6 year old fuel tank down to the bottom.

Thank you for any thoughts and ideas.

 

[Bosunsmate]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Ground your plug wires and then turn the engine over a few times, then pull the plugs to check they are all getting wet with fuel.

Turn the engine over enough to get water coming out the telltale as you need to get water into the engine to make sure that water isnt causing the fault.
Light it with a match to make sure its fuel and not water from a blown exhaust gasket getting water onto the plugs.

Sounds like carp arent wanted there like they arent here, they poisoned a lake here once to get rid of them

 

[boobie]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Check your spark with an open air gap spark tester set at 7/16".

 

[stumpknocking]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Thank you for your responses. Last last post disappeared??

Carbs cleaned again and the jet was cleaned this time. New plugs, Blew back the fuel line into the tank. The back pressure offered a refreshing gas shower along with some klumps of what looked like grease.

The number 2 cylinder looked weak on the spark test.

Compression is Top #1 125 psi #2 135 Psi #3 130 psi.

JUst hooked up rabbit ears fired right up. Throttled up a little and DANG if it didn't start the missing really bad again.

PIcked up a new Coil for #2 ,only to find when I got home it has two contacts instead of one like the old one.

Wish I knew how to attach a video. To a trained ear I feel it would be a simple fix.

Thanks!

 

[Bosunsmate]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

JUst hooked up rabbit ears fired right up. Throttled up a little and DANG if it didn't start the missing really bad again.

Thanks!

Is it idling ok? and just missing at throttle movement?

 

[stumpknocking]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Yes, It starts and idles fine. When I throttle up is when it starts coughing and missing really bad.

Before all the previous attempts to fix it was rough idling as well.
Thanks!

 

[racerone]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Have you checked the flywheel key ??

 

[stumpknocking]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

I haven't. I will look it up and check it out. Thank you!

 

[Bosunsmate]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Carbs cleaned again and the jet was cleaned this time. New plugs, Blew back the fuel line into the tank. The back pressure offered a refreshing gas shower along with some klumps of what looked like grease.

Did you lean your tank?
Did you check all passage ways behind jets a clear and all othe little passageways are as klumps will fill them up

 

[stumpknocking]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

I didn't clean the tank. It's mounted in console. I did blow the lines back to it and put a filter on the fuel line between the bulb and the engine.

http://youtu.be/oK0WjZS0R1Q


Here's the link to Youtube. It runs fine at idle which is much better than now. I've lowered the idle RPM.

As you can see when I throttle up she doesn't respond well.

 

[Bosunsmate]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Cant tell in the video-Is your timing base moving?
You can check with engine off

 

[Bosunsmate]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Whats that sound at 8 secs?
Turning key wrong way?

 

[stumpknocking]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

I'll check the timing base. Thanks!

The sound at 8 secs was part of the miss fire. The one at the end was me, thought I deleted the long string of four letter words………

 

[stumpknocking]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Timing base is solid.

 

[Bosunsmate]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Seems like 8secs is when you move it back into gear too
If you dont touch the throttle will it ever misfire/backfire at idle?

 

[Bosunsmate]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Timing base is solid.

Does that mean moving or stuck fast?

 

[Bosunsmate]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

It should move as you advance the throttle

 

[stumpknocking]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

When the throttle is engaged is when the miss firing begins. You are correct, that is the sound of me backing off the throttle.
At this time it purrs like a kitten at idle.

 

[racerone]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Is the timer base under the flywheel rotating as you advance the throttle.----Folks would like to know, does it turn --Yes or no ???

 

[Bosunsmate]

Re: 1983 Johnson 75 Hp started running rough and dies. Misses heavily under load.

Is the timer base under the flywheel rotating as you advance the throttle.----Folks would like to know, does it turn --Yes or no ???

Ha ha, im glad someone picked up that it was a question.