more old Johnson problems

milmo1 · Nov 16, 2009

Back in spring, i had some trouble starting my 20 hp 1966 Johnson outboard. It is a pull start, tiller drive btw.
After many attempts, including replacing the points and condensers, adjusting the timing cam, and using a carb off a parts motor, I was able to start and run the motor in a test can. I did however, have to manually blip the throttle roller to keep the idle strong. I never did get the chance to run her on the open water.

This weekend, I launched the boat. The old motor gave me some fits at the dock, as it would take 3 or 4 pulls, run for 3 seconds and stall. Then 3-4 more pulls, run and stall. As it struggled to maintain an idle, it would also make a horrendous knocking noise, which I thought might be the recoil mechanism as the motor shakes violently just before stalling. After appx 12 times, I was able to maintain idle - but it was running on one cylinder for a short time.

So, we motored out at a nice low cruising speed, maybe 1/4 throttle. I twisted her open, and nothing. Just the same low speed cruise. After 15-30 seconds - BAM. She'd take off like a raped ape. However, if I backed down to 3/4 throttle...we dropped back into that real low cruising speed. Open her back up, and 15-30 seconds later she would fly. Over and over again I repeated this.

I just don't know what to think?

Any ideas?

Thanks all.

bktheking · Nov 16, 2009

Re: more old Johnson problems

You are intermittantly firing on 1 cyclinder, that's why it was a PITA to start and why it would take off like a "raped ape" lol. Something is going on under that flywheel be it coil alignment, a wire shorting or not making contact, a bad coil, something electrical by the sounds of it.

Mas · Nov 16, 2009

Re: more old Johnson problems

Get a spark gap tester and see how far the spark will jump. Also, run the motor in the dark and see if the plug wire etc are grounding out by the presence of an errant spark.

mas

samo_ott · Nov 17, 2009

Re: more old Johnson problems

Mas said:
Get a spark gap tester and see how far the spark will jump. Also, run the motor in the dark and see if the plug wire etc are grounding out by the presence of an errant spark.

mas

Running in the dark works well. To make it work even better, get a spray bottle of water and mist the wires... You'll see in a hurry if they are arcing through anywhere.

milmo1 · Nov 17, 2009

Re: more old Johnson problems

I have checked the spark, and it is thick and blue. I have not tested how far it will jump. I did replace the points and condensers, but not the coil.

It will run on one cylinder at times, but not often. When I was in the "low speed cruise" it was smooth - firing on both cylinders. Then it would suddenly take off without rhyme or reason.
Someone told me I may be sucking air through a fuel fitting - any thoughts on that?

lindy46 · Nov 17, 2009

Re: more old Johnson problems

Sounds like a coil heating up and cutting out. I'd replace the coils and the wires.

oldrudedude · Nov 17, 2009

Re: more old Johnson problems

You replaced the carb. Did you do a link/synch?

My thoughts: If your spark checks out ok, the "hesitation" you are experiencing could be a "lean running low speed carb circuit" issue (or improper timing). When you give it throttle, the lag occurs as the vacumn builds up enough to draw fuel through the high speed jet --> then it takes off. Try adjusting the low speed needles out a bit.

Mas · Nov 17, 2009

Re: more old Johnson problems

Try running it without the hood. Maybe you're got an exhaust leak & it's choking for air??

Mas

jbjennings · Nov 17, 2009

Re: more old Johnson problems

milmo1 said:
I have checked the spark, and it is thick and blue. I have not tested how far it will jump. I did replace the points and condensers, but not the coil.

It will run on one cylinder at times, but not often. When I was in the "low speed cruise" it was smooth - firing on both cylinders. Then it would suddenly take off without rhyme or reason.
Someone told me I may be sucking air through a fuel fitting - any thoughts on that?

I also think it's a bad coil, and it may seem to run smooth on on 2 cylinders, but the sudden take-off is when you get the 2nd cylinder actually making power. The coils on that motor are common problems.
JBJ

milmo1 · Nov 18, 2009

Re: more old Johnson problems

Although I replaced the points and condensers, I did not replace the coils.

I did not link/synch the carb. I'm guessing that procedure is in the top secret files above this forum. I will do this if I can figure it out.

I found my spark "jump" tester, I will check the spark health.

Then I will report back.

Thanks all.

mikesea · Nov 18, 2009

Re: more old Johnson problems

Those coils will give fits if old.They can leak when hot,or when they just feel like.However,if your spark is good as you say,did you do the old squeeze the ball trick to elimate the possibility of a fuelpump problem?

milmo1 · Nov 19, 2009

Re: more old Johnson problems

Last night I did the spark jump test in the dark. I'll be darned if that lower cylinder wasn't firing regularly. On any given pull, I may get 2 sparks, 1 spark, or none at all. Then I extended the jump distance. The top cylinder gave me 2 consistent long sparks. When I tested the lower cylinder, I think I got 1 long spark in 5 pulls.

I'll post again after coils are replaced...

Mas · Nov 19, 2009

Re: more old Johnson problems

It's amazing what a $10 tool will tell you!

Mas

14ftgrumman · Nov 20, 2009

Re: more old Johnson problems

If you have 1 bad coil, replaqce them both,and the plug wires. Use only solid copper core wire. Hard to find, but if you tell the car parts guy that you need a universal set for a 4 cyl farm tractor, you should be able to get all the wire and associated stuff. For God's sake, don't tell him it's for an outboard, he'll tell you that he doesn't have marine parts.

samo_ott · Nov 20, 2009

Re: more old Johnson problems

14ftgrumman said:
For God's sake, don't tell him it's for an outboard, he'll tell you that he doesn't have marine parts.

Heh. Funny, but true! I get mine at the OMC dealer though.

steelespike · Nov 20, 2009

Re: more old Johnson problems

They may have the wire kit right here at iboats.18-5225 NAPA does carry the kit in their 600 page Marine Products catalog.18-5225 Unfortunately some branches don't know about the catalog.

milmo1 · Nov 21, 2009

Re: more old Johnson problems

The fun continues...

Replaced coil. Rechecked spark - great! Long blue and strong from both cyliders. Ran in a test can well. Took down to the lake, started right up, idled well. Backed away from the dock, motor died 50 feet away. Pulled it enough times to lose the skin on my hand, but only managed to get it to run a few seconds at a time.
Got it back home, won't start at all - but strong spark is still present. Pulled outgoing fuel line from pump - pumps nice with each pull on the starter cord.

??

Searched the top secret file for "link/Synch" - but don't see it...

Please Help...

bktheking · Nov 21, 2009

Re: more old Johnson problems

Try spraying some 50:1 mix into the carb and see if it fires. Could be a carb problem.

milmo1 · Nov 21, 2009

Re: more old Johnson problems

I think I have a carb problem, but I just got the motor to start and idle in the can. Since it is dark, I noticed a ton of arcing from the plug wires. I need to replace them. How do I access them for removal? My Clymer manual is pretty vague.

Thanks!

Maveric7383 · Nov 21, 2009

Re: more old Johnson problems

Napa sells the solid core wire by the foot, im sure they also sell the terminals too, and if your lucky they might have the crimping tool is stock too. the only other car place that might sell something like that is carquest.

more old Johnson problems

Seaman Apprentice

Vice Admiral

Lieutenant Commander

Vice Admiral

Seaman Apprentice

Captain

Chief Petty Officer

Lieutenant Commander

Captain

Seaman Apprentice

Lieutenant Commander

Seaman Apprentice

Lieutenant Commander

Chief Petty Officer

Vice Admiral

Supreme Mariner

Seaman Apprentice

Vice Admiral

Seaman Apprentice

Cadet