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1973 johnson 50. Starts then stalls when not in choke, any help be appreciated!

S

steve044

New member
Can anyone help on this problem I have. Purchased boat with unknown condition of engine. The engine turns over. First thing I seen was a bad gas tank, the gas was brown and rusted and water and just could tell it was sitting sometime. I Purchased a new tank and cleaned the fuel hose out the best I could, now this would fire up under starting fluid then stale. After new tank of gas and cleaned out carburetor the best I could, it would fire up and run with choke on and then stale if I let turned off choke. Now I bought a new kit and used some of the pieces and rebuilt the carburetor, even soaked the upper and lower carbs in a cleaning fluid for 2 days. I put the carburetor back on and pumped some gas into it. It will stay running with the choke in the start position that's located near the throttle in the front of the boat. It will run and sound good whej choke is on, as soon as I go from the start to run position on the lever it stalls. I'm going to try and readjust the idle needles as I seen in another post about how many turns he did. So fresh gas. Cleaned out fuel lines, it has spark, clearly it will run but not without choke being on, I'm not sure what else to check, this seems to be fuel related.
 
My 90 horse evinrude was doing the same thing and the carb was FULL of muck. Had jets cleaned all new carb kits installed took care of the problem.
 
Sfox said:
My 90 horse evinrude was doing the same thing and the carb was FULL of muck. Had jets cleaned all new carb kits installed took care of the problem.
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I just rebuilt the carburetor and I still had the same issue. Just found out I also had a small leak in the fuel pump assembly, hopefully this new pump will fix the problem. Did you fix it yourself or a shop?
 
I have a guy that has done this before he has the fine needle size tools to clean all the ports in the carb. He rebuilt them both from kits I ordered off of an Evinrude site. Here is a couple pics of the crap pulled from carbs. lol bad! This motor had sat a couple years
 

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I'm a noob, but I'll throw this in ....You said a new tank, but also put some new lines on it maybe ? Especially if it's that silver fuel line, the inside linings disintegrate over time, Fine particles could be plugging the fuel screen at the intake of the fuel pump, clean / check that too ?
Not related, but give it some brand new spark plugs too.
 
A 1973 motor has an electric choke solenoid the retracts & pulls the 2 chokes closed when it is electrically operated. If this boat has the original control box this is done by lifting a toggle switch just under the key while cranking. After the engine starts, you can toggle the switch as required to keep it running during the warm up. Typically just a few times is all that is needed.

That being said, this is taken directly from your opening post above:

"It will stay running with the choke in the start position that's located near the throttle in the front of the boat. It will run and sound good whej choke is on, as soon as I go from the start to run position on the lever it stalls."

The lever that lifts upwards approximately 45 degrees advances the throttle. IT HAS NOTHING TO DO WITH ANY CHOKE CONTROL. As you lower this lever, the carburetor butterfly closes & fuel metering transitions from the high speed jet to the idle circuit. YOUR CARBURETOR(S) ARE DIRTY!

Check for good spark on both cylinders. These engines will fire up & run poorly on 1 cylinder.

Check the link & sync. That is verify both carbs close completely, the cam follower roller is adjusted to begin picking up at the correct time, the spark advance linkage is correctly adjusted. These things don't typically go out of adjustment but are frequently missadjusted by unknowing do it yourselfers.
 
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gman206 said:
I'm a noob, but I'll throw this in ....You said a new tank, but also put some new lines on it maybe ? Especially if it's that silver fuel line, the inside linings disintegrate over time, Fine particles could be plugging the fuel screen at the intake of the fuel pump, clean / check that too ?
Not related, but give it some brand new spark plugs too.
Click to expand...
I haven't been able to find the outboard fuel hoses, there are 3-4 different sizes that are connected throughout the fuel and carbs and so forth. I just purchased a new fuel assembly but didn't realized I killed the battery so I'm waiting for that to recharge overnight. And I have changed spark plugs to being new. I did clean gje fuel lines out the best I could.
 
Droid said:
A 1973 motor has an electric choke solenoid the retracts & pulls the 2 chokes closed when it is electrically operated. If this boat has the original control box this is done by lifting a toggle switch just under the key while cranking. After the engine starts, you can toggle the switch as required to keep it running during the warm up. Typically just a few times is all that is needed.

That being said, this is taken directly from your opening post above:

"It will stay running with the choke in the start position that's located near the throttle in the front of the boat. It will run and sound good whej choke is on, as soon as I go from the start to run position on the lever it stalls."

The lever that lifts upwards approximately 45 degrees advances the throttle. IT HAS NOTHING TO DO WITH ANY CHOKE CONTROL. As you lower this lever, the carburetor butterfly closes & fuel metering transitions from the high speed jet to the idle circuit. YOUR CARBURETOR(S) ARE DIRTY!

Check for good spark on both cylinders. These engines will fire up & run poorly on 1 cylinder.

Check the link & sync. That is verify both carbs close completely, the cam follower roller is adjusted to begin picking up at the correct time, the spark advance linkage is correctly adjusted. These things don't typically go out of adjustment but are frequently missadjusted by unknowing do it yourselfers.
Click to expand...
I pulled off both carburetors and soaked them over night in a carburetor cleaner ( I can't seem to load pics on here) rebuilt them and reinstalled. Found out I'm out of gas and dead battery today so I'll have to wait another day. I'm not quite sure what the cam follower roller is?? Or the spark advance linkage? Is there a picture available for a view of this? The engine will run fine with earmuffs on but wont stay running in a tub of water completely submerged
 
You need a factory service manual.

It runs on muffs but not submerged because of exhaust back pressure. Trust me, it runs but not "Fine"
 
steve044 said:
Where and how would I check this?
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You would believe & trust us old timers that have many years of experience.

A 2 cycle engine does not have an exhaust stroke. It relies on exhaust scavenging thru the design. If you're only firing on 1 cylinder, it will run poorly but sound even to the untrained ear because it is firing at even intervals. Put any load on it, in this case exhaust back pressure or shifting into gear in a tub of water & it's done.
 
Also, are you sure you have a hot spark on both cylinders? Is compression good/within 10% between the 2 cylinders?
If yes above, maybe only 1 carb is plugged up. Get it running on the muffs & pull 1 plug wire off. Engine die? Any change in sound?
Repeat on other plug.
If 1 plug has results & 1 does not, go back into the carb for the dead cylinder.
 
Droid said:
Also, are you sure you have a hot spark on both cylinders? Is compression good/within 10% between the 2 cylinders?
If yes above, maybe only 1 carb is plugged up. Get it running on the muffs & pull 1 plug wire off. Engine die? Any change in sound?
Repeat on other plug.
If 1 plug has results & 1 does not, go back into the carb for the dead cylinder.
Click to expand...
I don't have any tools to try a compression test 😕 and now when i go turn the key it just clicks and don't do a thing...
 
I just re-read way above about not being able to find the fuel line hoses/sizes..... Snip off a little quarter inch piece from each size line, take down to your local Napa auto, have them match up........be sure and ask for fuel line, not vacuum line.
 
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