1993 Johnson 48hp dies at 1900 rpms

[roscottjr]

Model J48ESLETE

Engine starts and idles great. Runs great under 1900 rpms in and out of gear. Once it gets slightly over 1900 just under 2000 the engine dies. It doesnt sputter and die but dies like you turned the ignition off. Carbs have been fully cleaned, tank cleaned, new fuel lines. Even tried a different tank. Cannot get the engine to or over 2000 rpms. Could this be an issue with the primer system on the engine? The primer bulb stays hard ond doesnt get soft like the fuel pump wasnt working. Have also tested the fuel pump to be sure it is working.

Any help greatly appreciated.

Robert

 

[roscottjr]

Re: 1993 Johnson 48hp dies at 1900 rpms

any ideas?

Robert

 

[roscottjr]

Re: 1993 Johnson 48hp dies at 1900 rpms

noone has any ideas at all?

tried again today, started all over. tried engine, idles fine, give throttle and it bogs then shuts off at around 1900 rpm but will bog and shut down within a minute or so if left at 1200 rpms.

cleaned carbs- no change

cleaned fuel pump- no change

checked and cleaned primer system- no change

cleaned all fuel lines from tank to carbs- no change

cleaned everything at once- no change

tried a know good fuel tank and fuel- no change

The engine gives same results whether it is in gear or in neutral.

Robert

 

[roscottjr]

Re: 1993 Johnson 48hp dies at 1900 rpms

Have I got a 1 of a kind engine? Does noone know anything about this engine?

Robert

 

[roscottjr]

Re: 1993 Johnson 48hp dies at 1900 rpms

Ok, I narrowed the issue doen to 1 of the carbs. After disconnecting the plug wires one by one and checking spark as well I found the bottome cylinder was getting no fuel. I have cleaned the carbs on this engine 5 times now so I know without a dought both carbs are getting fuel. In hopes that maybe the bottom carb was bad I switched the carbs and just as I expected now the top cylinder is not getting fuel so I know without a dought it is the carb. When I cover the front of the carb with my hand it will pull gas in and run fine but only if the front of the carb is completely covered. The boat sat for about 2 years so the first thing I did was clean the carbs and then rebuilt the one thats no working but to no avail.

I have cleaned every nook, cranny, passage, port, and every other part of the carb 5 times and still getting nothing from the carb to cylinder. The carb is getting fuel to the bowl but its like it dont want to let it pass to the cylinder. Due to the issue and the cleaning and carb rebuild not helping I purchased a new carb and will update when I receive it.

Anyone know what may be going on with this carb? Is it possible for a carb to just go bad and cant be fixed? I do all my own mechanical work on my vehicles and boats and also do auto mechanic as a side job but have never run into anything like this before. Usually after a rebuild they work fine but this one is being extremelly stubborn.

If anyone knows what the problem may be I would be extremelly thankful for the info.

Thanks
Robert

 

[mikesea]

Re: 1993 Johnson 48hp dies at 1900 rpms

Ok,your tests show a %95 its the carb.How did you CLEAN the carb.The smallest piece of trash can stop performance,Iy should be throughly soaked in a carb cleaner that can be purchased at Nape,Auto zone and like auto stores,I like to spak em overnite ,be sure all rubber and plastic is removed,I then use dish detergent in hot water for a cleaning soaking,,wash with hot water from sink ,then compressed ir if possible or a can of aerosol carb cleaner blown through all the passages,I also recommend changing the needle and seats,dont recall the needle valve on that eng,but screwing it in and counting the turns should give you your setting.I believe its 11/2 turns.Be sure your timer base under the flywheel is rotating properly with the throttle advance arm

 

[roscottjr]

Re: 1993 Johnson 48hp dies at 1900 rpms

That sounds like the steps I took when cleaning it. Like I said, Ive never seen a situation like this before. Ive used everything from cleaners to different size wires to make sure all passages were clear and yet it still doesnt work. Ive never had a carb just go bad but Im starting to think its possible.

Yes Ive checked the timer base as well as the engine timing and all linkages. Everything is strictly "by the book" with the exception of the 1 carb not allowing fuel to pass.

Robert

 

[mikesea]

Re: 1993 Johnson 48hp dies at 1900 rpms

I have seen bad caebs.Usually having to do with the butterfly rod wallowing out the hole it goes through and the pick up tubes having issues.Fortunatly we had spares and never got to into the why's of the problem.The fact that you say It just guits like the key was turned baffles me.Is there any possibility that a wire in a control box is grounding at a certain point?like a neutral safty .Even losing a cyl.would cause sputter and stil probably run.Primer would likly cause more trouble at idle ,too much fuel.It almost sounds like a total loss of spark.But why ???Hope someone comes up with it.I'll keep my thinking cap on.Be sure to let us know.Back again.I really think after re reading.Your carb has an issue in the pick up .If other carb works,and manually choking helps,carb is getting fuel,then carb dont seem to be delivering fuel.I would have thought reeds ,but switch of carn proved not reeds.Its gota be the carb,in the fuel delivery.

 

[roscottjr]

Re: 1993 Johnson 48hp dies at 1900 rpms

New carb came in today and engine is now running great.

Thanks for all the help.

Robert