50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up HELP

[browns]

50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up HELP

i have a 50 hp johnson, 1972... would start ok...after running it on the water for about 10-15 minutes, it conks out... then i try to start it... turns over, but doesnt' fire... after letting it sit for about 10 minutes it will start up...

i had it in the repair shop... impellar, thermostat, power pack, rectifier...replaced...still does it... also as a side note, the battery does not stay charged long......any ideas...i am a very new novice with little knowledge, but i am a quick study... any help would be great...

 

[JB]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Howdy Browns.

Welcome to iboats.

First thing is to determine whether it is losing spark, overheating something or running out of fuel.

Second is to remember that mass changes of parts is the most expensive and least effective troubleshooting method known to man. Find out what is wrong first. Then replace the failed part.

Is it runnning out of fuel?
After it has "conked out":
If you pump the primer bulb will it start?
If you squirt some fuel premix into the carbs will it start?
If you loosen the cap on the fuel tank, does it whoosh?

Is some part failing from heat?
If you use a hair dryer (not a heat gun) to heat the coils when the engine is cool will it still start?
If you remove the cowling before setting out does it still "conk out"?

Is it losing spark?
If you remove a spark plug wire after it "conks out" can you get a hot, blue spark of about 7/16" from the plug wire to the block?

If the above doesn't make the fault obvious, let us know what you find and we will get you humming again.

 

[HighTrim]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Check the cranking RPM. A cranking speed of less than 250-RPM will not allow the system to spark properly. This could be due to your weak battery. Start by having it load tested to check the integrity of it. It may be as simple as a new battery. If it checks out fine, look into the charging system. Also perform a spark and compression test and let us know what you find. Welcome to iboats.

 

[browns]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

tx for the great responses... i will give it a whirl this weekend... and repost with my results... another person told me that one of the coils may be grounding out when it gets hot and to check the grounds... also possibly fuel problem/fuel filter... so i have alot to go on... any idea why the battery needs a tricke charger on it...at all times... the battery is new... seems like it is not being recharged....
tx again folks...

 

[HighTrim]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Your alternator is obviously not working properly. This could be due to faulty wiring, rectifier diodes damaged, shorted or open stator windings, or the regulator damaged. Do you have a manual to test these?

 

[rolmops]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

tx for the great responses... i will give it a whirl this weekend... and repost with my results... another person told me that one of the coils may be grounding out when it gets hot and to check the grounds... also possibly fuel problem/fuel filter... so i have alot to go on... any idea why the battery needs a tricke charger on it...at all times... the battery is new... seems like it is not being recharged....
tx again folks...

That other person is known around here as rolmops

 

[HighTrim]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

I would start by checking the wiring and connections, polish them until they shine. After that test the stator. Disconnect the yellow lead and yellow /gray lead at the terminal block. Connect the red meter lead to either yellow lead and meter black lead to ground to check for shorts. An infinite reading on HI ohms scale indicates the windings are good. Connect the ohmmeter on LO ohms scale beetween the yellow and yellow/gray. A reading of .25 ohms + or - .1 indicates the windings are good, and an infinite reading indicates the windings are open. If windings are found to have failed, the stator must be replaced.

 

[HighTrim]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Or if you have an ammeter, disconnect the voltage regulator at the terminal block. Run the motor at 4300 to 4600 RPM and note the ammeter reading. SIDE NOTE: Disconnect all accesories. If the ammeter shows charge, replace regulator. If ammeter shows no charge, check rectifier and check stator windings as described in the above post. The rectifier is tested with the ohmmeter on HI ohms scale. High reading on one check and low reading on the other, the diode is ok. Zero reading on both checks, diode shorted. High reading on both checks, diode open. Good luck.

 

[domains]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Could be a coil ...they work best cold ...could be carb valve sticking ..could be when motor is warm piston rings loose compression . clean carb ..pump primer when driving could be fuel pump . check plugs could be cabon closing gap ..if points not sure could be burnt or not set .

if coils when hot ...unplug one spark plug wire at a time see which works best ..don't throw your money around.

 

[domains]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

oops is it pumping water? if thats your prob johnsons can overheat no probs ring gaps ..just replace gasket head and water pump.

 

[browns]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

yes, it is pumping water... one of the things that was taken care of during a recent repair was that there was gravel in the uptake hose... overheated, thermostat was melted...as i was told... (but it didn't look melted)...new thermostat, pump impellar, but i will say that the motor ran with more powere after this was replaced... compression in both cylanders was 180 each one...

 

[tashasdaddy]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

the run 10 off 10 leads me to coils, or power pack. had same problem with 73 50hp. it was the power pack.

 

[browns]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

i replaced the powerpack myself and it still did the same thing... didn't try the coils... i will take a look at that...
tx

 

[tashasdaddy]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

there are the such thing as bad new power packs,
elect testing here 6 pages find your motor. "http://www.boatpartstore.com/page28.asp"

 

[rolmops]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Do try running it without the cowling (engine hood).It may be that you have an exhaust leak into the cowling and the engine becomes oxygen starved after a few minutes,which will cause it to conk out.

 

[browns]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

had the boat out today... ran great for approx 10... and conked out... waited 5 minutes, and started... took the cowling off, and cruised with the boat for 15 minutes, and it DID NOT conk out....

 

[JB]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Okay!! You have a part failing from heat.

Next is to put heat on the ignition system. . .stator is prime suspect. . .and see if she will still start. If it were a coil you would only lose one cylinder.

 

[HighTrim]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

I would start by checking the wiring and connections, polish them until they shine. After that test the stator. Disconnect the yellow lead and yellow /gray lead at the terminal block. Connect the red meter lead to either yellow lead and meter black lead to ground to check for shorts. An infinite reading on HI ohms scale indicates the windings are good. Connect the ohmmeter on LO ohms scale beetween the yellow and yellow/gray. A reading of .25 ohms + or - .1 indicates the windings are good, and an infinite reading indicates the windings are open. If windings are found to have failed, the stator must be replaced.

If you have an ohmmeter you could try the above test.

 

[rolmops]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Hello Brown.
Sorry for not being able to come and see you today.
It sounds like you have most of your problems licked.
The easy way to check out if your stator is the cause of your trouble is by heating it up with a hair dryer.Just blow the hot air under the flywheel for a few minutes and then try to start up.Also make very sure that the wires from under the flywheel are well insulated and all the connection are clean and snug.You can also do the ohm meter thing,but only right after it conked out on you.
As for exhaust leaks,just lay the cowling without tying it down so there is sufficient air replacement coming in and make sure the air intake holes in the top and bottom cowling are wide open.
As for the battery drainage problem.The old outboards really do not produce a lot of electricity and in order to charge your battery you really have to run the engine at a high rpm (somewhere close to wide open throttle) for a while in order to recharge ,this you can probably not do in the canal.
Take the boat to the bay and run it fast for a while, that should charge your battery.
Again ,sorry for not being able to come and see you in person,but that is one of the drawbacks of my line of work.

 

[JB]

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Re: 50 hp 1972 johnson, runs for about 10 minutes &conks out, wait 10 min. starts up

Got this PM from browns. My reply is included.

hi, tx for the feedback...your recent comment suggests putting HEAT on the ignition...what do you mean...? how do i do that? is it done with the engine running, cold, etc.... the stator elec. check with the ohmeter... i believe i can do that with my very basic beginner information... but the heat ono the ignition system...what does that entail... tx tom

Use a hair dryer, Tom. heat up the ignition area on the cold engine and see if it causes it to quit or refuse to start.

The Ohmmeter test won't tell you anything on a cold engine; it works when it is cold. It is when it is hot that it quits, and it seems to be a fine line. . .if you take the cowling off it stays cool enough to work.

This communication needs to be in the thread, not in a private message. That is how other readers learn.