1990 johnson 48 spl it did something weird

[smvarner]

It still won't start in water haven't tried it on muffs since the other day when it ran away. Tried to start today and would only start and run for a few seconds if I squirted a little gas in the carbs but would not stay running and would only start if I squirt gas in the carbs will try more tomorrow starting to think something was missed in the carbs when cleaned

 

[oldboat1]

You can safely run on muffs. Just don't run above idle/fast idle.

There is a problem if it will run only on muffs, but at least can do some troubleshooting. Do the drop cylinder test. Monitor operating temp, and work on the carb idle adjustment needle. If you can get it idling smoothly on muffs, go back to testing in your barrel.

At some point, I think you will want to see if it's charging, having disconnected the battery while running.

 

[jbuote]

Scary (memorable, but rare). Best way to stop it is to cut off air -- jam a shop rag into the carb throat(s) on motors without an air silencer, otherwise the silencer intake.

Not saying it would happen, but if you're at all worried about a possible runaway again when you run with muffs, then don't forget to have some rags handy "Just In Case" as already mentioned above...

 

[smvarner]

Hi all did some work today and i think i have the problem found pull the spark plug wire off the top cyl. stays running pull the bottom and it shuts right off if i hold my hand or a rag over top carb and pull the bottom plug wire off it would stay running move my hand or rag away and it shuts right off i have the carb in question off and pulled apart but dont see anything that stands out as a problem will soak it in some carb cleaner again and pick up another carb kit then see how it does

 

[Bosunsmate]

You can also swap the carbs over and see if the problem follows the carbs. I find carb cleaner doesnt do the whole job, only blowing carb cleaner through every hole and checking it comes out another hole with just as much force is the only way to check every passage is clean. If there is a suspect one, put a soft copper wire up there and id safely bet you will push through a big globluar scab that is causing the issue.
Dont forget to consider that the top seal might of gone and using your hand is allowing just enough of a rich fuel mixture to get drawn in, but carb seems more likely

 

[smvarner]

Hi after looking the carb over and talking to my local dealer I have found the problem the carb has a cracks in the brass tube going into the float bowl was told it's called an emulsion tube by local dealer and it couldn't be replaced. Was told the cracks will cause it not to pull enough gas up from the bowl he said if i really wanted that carb fixed i could try and fill the cracks with silver solder but was hard to do with it being so thin. So I ordered a used set from eBay and kits for both for $90.00 between them all I should have a working set. I should have known to look for that earlier had the same problem a few years ago on a 77 evinrude 6hp. new carbs will be in next week I'll let you all know how it goes thanks

 

[Sagerider]

You stated in post#1 that you pulled the spark plug wires off and the engine continued to run, obviously this should not happen. Contributing factors, heavy carbon build up on cylinder head, incorrect spark plugs that are too hot and act as glow plugs the same as a model airplane engine. Check your spark plugs as being correct for your engine. There must be an ignition source and since you pulled the spark plug leads off there must be something else igniting the fuel air mix in the cylinders. Carbon build up deposits can and will heat up hot enough to glow and act like a glow plug if heavy enough. Being a rebuilt engine I doubt that it is carbon deposits on the cylinder head. That leads me to the plugs are not correct for your engine.
Let us know if they are correct or not correct and condition please.

 

[smvarner]

Spark plugs are NGK B9HS10 and they are new

 

[Sagerider]

But are they correct for your engine.

i am an old two stoke sort of guy from way back but just not outboards and this is why I am interested with your issue,
you got it fixed, right ?

 

[smvarner]

That is the plug given in the repair manual I have for NGK and I'm waiting on a set of carbs to come in so I can replace the one with cracks in the emulsion tube the brass tube that goes onto the float bowl nex Wednesday is the delivery date hopefully it comes in sooner my aunt told me the same as you about to hot of a plug can keep a 2 stroke running after turning the key off she worked on dirt bikes a lot back in the day if it happens again I'll go to a colder plug

 

[Sagerider]

Tell your aunt I said “Hey”

 

[smvarner]

The carbs come in on Saturday no rebuild kits yet should be in mail today I went on and dropped the carbs in some cleaner and tried them out motor started up pretty easy with a little bit of a miss did some adjustments on the idle screw and that went away this was on the muffs. Then I moved on to the test bucket with a little more adjustments to the idle screw IT RAN IN WATER sounded the best it ever has. Ran good for a while then would not idle the carbs picked up some piece of trash which I confirmed today when I pulled them all the way apart for a good cleaning after the carb kits come in I'll report back with how it did

 

[ob]

If you can confirm that your engine is indeed a 1990 48 horsepower , the proper sparkplug for that engine is a Champion QL78YC gapped at .030. This plug has a protruding nose electrode and the placement it provides in the combustion chamber is critical to the engines smooth operation.

 

[smvarner]

hay ob yes the motor is a 1990 johnson 48spl model J48ESLESA i think to local part house cross referenced the right ngk plug will check again to make sure i dont normally use champion plugs have had to many of them just stop working for no reason. but i did have to use them on a 1960 johnson 3hp seahorse the ngk were to hot of a plug for that motor. so we toke the boat out for a test run it did prety well had a little problem when slowing down it suddenly died started back up after what could cause this i know it still needs some adjustment but the tide was going out so back in we went will try again when i can btw the plugs i have are gapped at .030