1981 Johnson J50BECIC not starting, stalling - suspect carb, please advice

[Carmageddon]

Hello!

I have the Johnson J50BECIC engine.
Since I bought the boat, I am having issues starting (may have started having those since I didn't initially follow the correct startup instructions I was given, but anyhow..) up the engine, and when it works, at WOT, after a while it just lost power for like 30 secs, and then shut down without me being able to start it back up (had to paddle!).
Other times when it starts, when I'd take slowly the choke down, it would stall and shut down about 1/3 way to close position.

I did some diagnostics, with a lot of help and advice on Reddit, I bought spark plug tester, and when trying to start, can see the light flashing in both cylinders, new spark plugs as well (NGK), so I think we can rule out the ignition system.

I had old fuel, I got it out and replaced with Super gas instead of regular.
I opened the carburetor air intake case, and sprayed in carburetor cleaner in while running on land (with water intake connected to cool the engine) - it was running fine for maybe 20 mins.

So next day, I took it to the lake, and surprise - it didn't start again!
Some Nice Guys who have much more experience and knowledge than me, tried to help me out, we tried to start it with different checks, but they noticed that there is way too MUCH gas in the water, speculating the ignition chamber is flooded with gas and sparks are unable to ignite it - I didn't have the wrench with me on the water.

But as per their suggestion, when I got back home, I tried starting again - having the same issue of not starting;
I then removed the spark plugs (didn't see much liquid, maybe it evaporates quickly, dont know) - I used compressed air from my compressor, to clean and dry the plugs thoroughly, as well as the ignition chamber though the spark holes.
I reassembled it all, and it started immediately!

After a minute or two idling, I turned it off, and tried starting again - this time again, it stalled when I got choke to 1/3 or so.


So, based on all that I've been told, it seems I have two issues:

1. Carburetor sends too much fuel into the engine - can I adjust this without taking the carburetor apart? If not, How to clean it? I have a kit coming in a few days, but the videos I have seen online are not detailed and specific for this engine.. I still don't feel confident doing this.
2. There may be some grain of dirt or something in the bowl, and when in WOT, that something intermittently gets stuck in the jets or something, and that causes the 30 secs lower power output at WOT, when it finally dies.
   This theory made sense, until the above theory was kind of confirmed with me venting the spark plugs with air... on the other hand, this one may still be the reason for the WOT issue so need to clean the carburetor anyway?

I guess I kind of mixed in the question with the possible causes above.. I am looking for opinions, does the above sound right? Anyone knows where to get the service manual for that engine? Or one that is very close to this engine?


Thanks guys!

 

[oldboat1]

Use Champion L77JC4 plugs, gapped at .030. Bite the bullet and rebuild the carbs (oem kit is 0396701, which comes with float and probably instructions). Completely disassemble and soak top and bottom. Remove the domed plug on top and clean idle passages. Leave all lead shots in place, along with assemblies like choke and throttle. I soak in lacquer thinner, then clean EVERY opening with soft wire, and blow out with carb cleaner, using the plastic nozzle. Air dry.

Use an open air tester to measure ignition strength:

 

[racerone]

edited

 

[racerone]

I believe the choke is activated by pushing the key in.-----Why do you say----" when I slowly take the choke down "----- on this motor ?

 

[Carmageddon]

I believe the choke is activated by pushing the key in.-----Why do you say----" when I slowly take the choke down "----- on this motor ?

There is a choke handle - I attached a picture.
When I start it, I have to open it full, and then its revving (if it starts), and I have to slowly, gradually reduce it to closed position.
If I dont close it, I cant engage the throttle.
The problem is, sometimes 1/3 of the way or so, the engine stalls before I fully close it (in other words, I close maybe 2/3 before it stalls)

Hope that is clearer now?

 

[Carmageddon]

Use Champion L77JC4 plugs, gapped at .030. Bite the bullet and rebuild the carbs (oem kit is 0396701, which comes with float and probably instructions). Completely disassemble and soak top and bottom. Remove the domed plug on top and clean idle passages. Leave all lead shots in place, along with assemblies like choke and throttle. I soak in lacquer thinner, then clean EVERY opening with soft wire, and blow out with carb cleaner, using the plastic nozzle. Air dry.

Use an open air tester to measure ignition strength:

Could you please explain a little more about the plugs, what does "gapped at .030" means? I just used regular wrench to remove and install plugs...
Should I replace the new NGK plugs anyway, specifically with the Champion ones you mentioned anyway, or is that for next season's replacement comment?

Also what do you mean "soak top and bottom" - in what? I read in carb FAQ in the site, I assume you mean in something like laquer thinner which some recommended? or what?

I have no idea what are domed plugs, lead shots.. that is why I am hesitant to do carb disassembly, as the videos and terms are not fully explained, they just show generic process. Do you know of any video that is close to the carb I have?

How best to disconnect it from the various links and levers, picture attached.

And thanks for your advice and encouragement! I would ask for some more until I feel ready (while also waiting for the cleaning kits to arrive this week, as its two essentially needed).

 

[racerone]

That is NOT a choke handle at all.----That is the " throttle only "----warm up lever.-----Choke is activated by pushing in the key !!------Read an owners manual or ask your local friendly boat shop to explain this all to you.-------I suspect trouble shooting is needed to find out what is wrong with your motor !!

 

[Carmageddon]

That is NOT a choke handle at all.----That is the " throttle only "----warm up lever.-----Choke is activated by pushing in the key !!------Read an owners manual or ask your local friendly boat shop to explain this all to you.-------I suspect trouble shooting is needed to find out what is wrong with your motor !!

ohh, I don't have a manual, its too old to have one LOL

I really have TWO sets of startup instructions, one from original owner, and one from mechanic who told me everything is fine and showed me that it works (that is, for him, it sometimes doesn't start for me..)

Original instructions were like:

1. Connect fuel hose to engine
2. Prime the pump until hard
3. key to ON, press on the key 3-10 times (depends)
4. Raise the handle up (the one I assumed is Choke handle, you call "throttle only"
5. Press key in, and turn to ignite.
6. Once the engine revs, take down the handle slowly

This process worked for the owner for years, my mechanic essentially told me the same, but without step 3 he says its not needed, and he also played a little bit with the throttle only position, until found like 3/4 open position where it started for him, so he said no issues.
The previous owner always turned off the engine by disconnecting the fuel hose, to drain the carburetor out of fuel to keep it clean, the mechanic told me no need, perhaps only at end of the season.

What do you think?

And thanks for the clarification! I really was guessing it is a "choke", like you had in old cars in the early 90's where you'd pull a handle to allow the engine to warm up, I assumed that is a choke of sorts..

 

[Carmageddon]

Use an open air tester to measure ignition strength:

I forgot to ask about this part - I saw something very similar, but I bought this to test the spark:
https://www.princessauto.com/en/deta...er/A-p8003334e
the light was blinking rapidly when starting so ignition works.

They also had this which is very similar to what you linked above:
https://www.princessauto.com/en/deta...er/A-p2990056e

I dont remember if I saw this one however:
https://www.princessauto.com/en/deta...er/A-p2990221e

How are those last two differ? Which one do you recommend I keep?

 

[Carmageddon]

Champion L77JC4

I just googled a little on this, I read that the QL77JC4 has better resistor to supress RFI and EFI interferences and is usually recommended for Marine applications.
Should I aim to get this one instead?
The reason I chose NGK over Champion was because they were more expensive, and I know of NGK being used in cars, so I assume must be better than a name I have never heard of before.. and thought I am buying quality plugs for sure

 

[jakedaawg]

I am surprised a compression test has not been mentioned. That's a must before spending any dollars. You never want to spray carb cleaner in a running engine. That's not what it's used for. There is no oil in it.

so,...post the results of a compression test.

 

[Carmageddon]

I am surprised a compression test has not been mentioned. That's a must before spending any dollars. You never want to spray carb cleaner in a running engine. That's not what it's used for. There is no oil in it.

so,...post the results of a compression test.

Sorry, must have slipped my mind when writing the OP!
The mechanic did a compression test, results were 130psi in BOTH cylinders, so that is very good

 

[racerone]

Pushing the key in before cranking is a waste of time !!------The key is to be pushed in while cranking the motor over.--------This has been the correct procedure since about 1980 when the primer valve was introduced.------I am always surprised when folks do not know how to start these motors.

 

[oldboat1]

Think this may not be your cup of tea. Try looking at some videos on outboard carb rebuilding (one similar to yours). Carb has a top and bottom. (bowl is on the bottom). Domed fitting is on top (replacement in kit). Remove to clean the idle passages. Get the Lisle open-air adjustable tester -- tests ignition strength.

 

[Oldnbold]

Does this model have a fuel diaphragm on the block?

 

[Carmageddon]

Does this model have a fuel diaphragm on the block?

If you mean a fuel pump that looks like https://www.amazon.com/Diaphragm-Evinrude-Johnson-Outboard-0438559/dp/B0719DD84Q, then yes.. we tested it by loosening the filter bolt, and fuel would come out when starting it up.

BTW, do you know which one fits this engine that I can buy which ships to Canada? Johnson dealer in Halifax says no kit for this, only whole new unit for 149 CAD (about 110$ US)!

 

[racerone]

Some will argue.-----These pumps are elegantly simple.----Simple to test.----Simple to repair.-----I would never ever spend $150 for a new pump.-----Only thing that might go wrong is the diaphragm.----Easy fix here.

 

[Carmageddon]

Some will argue.-----These pumps are elegantly simple.----Simple to test.----Simple to repair.-----I would never ever spend $150 for a new pump.-----Only thing that might go wrong is the diaphragm.----Easy fix here.

Where to get gaskets, new diaphragm for it, then?

 

[Oldnbold]

If the diaphragm has a hole in it, it will not only pump fuel into the carb, it will pump unwanted fuel right into the cylinder that it’s attached to causing a noticeable fuel sheen in the water. It’s not hard to take this pump off and disassemble and inspect the rubber diaphragm.

 

[racerone]

Step #1 would be to take it apart and see if there is something wrong with the diaphragm.---Then look at the various available kits for a match-------Also I can not tell from here if your motor still has the original pump !---Many, many pumps are replaced for no reason at all.----Perhaps desperation or a lack of trouble shooting--I can assure you this would be a simple fix on my work bench !!