79 johnson 140 wont start

hoodmekanik · Feb 15, 2013

Hey everyone I new to the thread but not to engines...

I have this boat with a Johnson 140... compression is 140 130 135 130, 6 gal of 93 with 17 oz of 2 stroke oil....

3rd new set of spark plugs... I started with ngk and now champions are in... I've got strong spark....

Carbs are clean with all new gaskets jets and needles...

Fuel pump is working

Reeds are intact.... none are stuck cracked or missing...

The boat ran 2 weeks ago... it idled and reved at the motor fine.... I put the prop on a huge bucket of water to put the engine under a load before I go out and register them and break down in the water...

It had power ran perfect I gave it full throttle once and slowly brought it back to idle and it shut off...

Ever since then I couldn't get it running....

I still have spark , same compression and new gas... I don't know where else to look...

Also the gaskets from the reeds up to the carbs are new

multimech · Feb 15, 2013

Re: 79 johnson 140 wont start

If everything is the way you have stated (not going to point my finger for BEiNG sure carbs are clean and etc.

) then I would check your base timing and also check to make sure that the idle needles are not set for running without any back pressure and failed once you did put back pressure to the engine. Could be real simple. You sound like you have a good handle on it. Also make sure you didn't pick up a bit of water in your gas.

hoodmekanik · Feb 15, 2013

Re: 79 johnson 140 wont start

multimech said:
If everything is the way you have stated (not going to point my finger for BEiNG sure carbs are clean and etc. ) then I would check your base timing and also check to make sure that the idle needles are not set for running without any back pressure and failed once you did put back pressure to the engine. Could be real simple. You sound like you have a good handle on it. Also make sure you didn't pick up a bit of water in your gas.

I have 2 desperate fuel cells filled with new gas cause I thought the same... and I'm even getting fuel on the spark plugs.... this is crazy.... and how many turns does the needle have to turned out from close

emdsapmgr · Feb 16, 2013

Re: 79 johnson 140 wont start

Your compression is strong on that powerhead. Try to start the engine. After 20 seconds, pull 2 or 3 plugs and see if they are wet or dry. That will tell you something. wet=no spark. dry=no fuel. While cranking, put an inductive timing light on each plugwire. The flashes from the gun will tell you if the spark is strong, intermittent, or weak, etc. The starter motor has to crank the engine at least 200-250 rpm's in order to fire the ignition system.

hoodmekanik · Feb 16, 2013

Re: 79 johnson 140 wont start

emdsapmgr said:
Your compression is strong on that powerhead. Try to start the engine. After 20 seconds, pull 2 or 3 plugs and see if they are wet or dry. That will tell you something. wet=no spark. dry=no fuel. While cranking, put an inductive timing light on each plugwire. The flashes from the gun will tell you if the spark is strong, intermittent, or weak, etc. The starter motor has to crank the engine at least 200-250 rpm's in order to fire the ignition system.

So the plugs are wet but I pulled them all out put them on each wire and crank with the ignition on and all 4 has blue spark... It seems like I'm not getting spark when the gplus are in... But I have a tester that im going to hook up individually to each wire and test to see if there's spark

hoodmekanik · Feb 16, 2013

Re: 79 johnson 140 wont start

I am using a red top optima battery and a battery charger... So it's at 12-14v all the time...

dwco5051 · Feb 16, 2013

Re: 79 johnson 140 wont start

Since you have good compression, fuel as indicated by wet plugs, and spark it should run. Unless the spark is not at the right time in the cycle or the spark is weak. Check with the spark tester with the plugs in and with a timing light as already mentioned. There is a remote chance that you may have sheared the flywheel key and you are not getting spark at the right time.

emdsapmgr · Feb 16, 2013

Re: 79 johnson 140 wont start

Sounds as if your should hear some firing.....Usually with a sheared flywheel key, good fuel and spark, you will get cylinder firing. It may backfire, but it should give some indication that it is firing. An inductive timing light is helpful, as it will give you a spark indication with the plugs in.

James R · Feb 16, 2013

Re: 79 johnson 140 wont start

May still be fuel. These beasts need a whole load of fuel to get them to fire. Try using a spray bottle with fuel mix and shoot into the carb throats while cranking. Be sure that the choke system is working correctly and that you open the throttle to start. If the choke isnt working correctly then it will not fire. If it fires using the spray, fuel supply is the issue.

hoodmekanik · Feb 16, 2013

Re: 79 johnson 140 wont start

I'm going to try with the timing light tomorrow and spraying with spray bottle... the choke has to be working cause when I let off from cranking and choking the carbs pour out the fuel out the carbs

hoodmekanik · Feb 17, 2013

Re: 79 johnson 140 wont start

So I tried spraying the engine with a spray bottle and nothing... I also used a timing light and checked spark at every cylinder... and I put a spark plug light on each wire and all 4 wires are sparking.... one thing I am getting is a light backfire and white smoke out the exhaust after cranking for about 20 secs... but no start....

emdsapmgr · Feb 18, 2013

Re: 79 johnson 140 wont start

Next step: Check for a sheared flywheel key.

hoodmekanik · Feb 18, 2013

Re: 79 johnson 140 wont start

OK ... I will take the boat to my shop to hit off the flywheel bolt off with the gun... now I've notice with the timing light w on 1cyl while cranking a little white dot on the flywheel appears before the timing tab ... is this correct

dwco5051 · Feb 18, 2013

Re: 79 johnson 140 wont start

Are there any numbers embossed on the flywheel close to the white dot? A picture would be a great help. Have you checked the intensity of the spark with a spark tester? A grounded plug will often show a spark when out of the cylinder but will not fire under compression like it should. That motor should have a spark of at least 3/8 to 7/16 of good bright spark in an air gap tester if my memory serves me correct.

emdsapmgr · Feb 19, 2013

Re: 79 johnson 140 wont start

Often a tech may put a white dot on a specific timing mark on the flywheel. On a running engine, it helps to highlight the specific degree timing mark that you want to time it on. (per the factory manual or label on the engine.) If you are checking the #1 cyl and aim the timing gun at the flywheel indicator marker, it should show specific degrees of timing on the flywheel face while cranking over. You may be able to determine if the flywheel key is sheared or not based on the observerd indicated degrees of idle timing-without removing the flywheel. Usually idle timing is around 4-5 degrees advance, but this is just an initial setting-before you set the idle when the boat is floating in the lake.

hoodmekanik · Feb 19, 2013

Re: 79 johnson 140 wont start

Wow everybody thank u for yoyr help.. I pulledthe flywheel off and the woodruff key was shredded... Unbelieveable... I put a new woodruff key n it fired right up... Thank you again

dwco5051 · Feb 19, 2013

Re: 79 johnson 140 wont start

Did it seem that the shaft had any form of lube on the taper? The shaft and flywheel should be squeaky clean when assembled. It is possible that the fly wheel was off sometime before and who ever removed it put some type of lube on it to make it easier to remove in the future. The key is to ensure proper alignment when putting together and the friction on the tapered fit and the proper torque of the nut should keep it that way.

79 johnson 140 wont start

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