Johnson outboard wont stay running

[steelhorse1369]

[h=2]97 johnson 40 hp wont stay running[/h] Today, 05:38 PM


97 40 hp johnson was running great, went from running full throttle to nearly a idle, i shut it off and it would start but die. figured it to be fuel pump that was a vro pump with oil disconnected, replaced it with a standard pump, capped off the old pulse line and ran all new fuel lines, took carbs off and cleaned and rebuilt them setting the initial idle jets at 1.5 turns from a soft seating. motor still starts and dies, will run around 15 seconds at idle and maybe 5 with fast idle in use ( turned them out 5 turns a half turn at a time same results ),. installed new spark plugs and getting bright blue spark. In line primer bulb is pushing fuel but will never get hard. I can also see fuel in the throat of carb when motor is tilted slightly. Im stumped , any ideas.
thanks, Mark

 

[flyingscott]

What is the compression? Did the motor overheat?

 

[boobie]

Agree, what is the compression ??

 

[steelhorse1369]

did not overheat , compression is 130 top and 115 bottom, dont have a spark gauge but each plug has visible spark

 

[fireman57]

Tank vented? Kink in fuel line? Can you squeeze the primer bulb and keep it running? If it keeps running with squeezing your fuel pump is weak/bad.

 

[jakedaawg]

The fuel running out the carbs and the bulb not getting hard points toward bad float, needle, seat issue.

I would double check installation. Some of the seats need a little fiber washer under them and if forgotten during reassembly you get issues like this. Also floats can sometimes be installed upside down on a few models. The little clip that holds the needle to the float arm could be missing. The float heigth could be wrong.

Primer bulb could also be partly to blame, they go bad and also need to be in a generally upright position.

 

[gm280]

steelhorse1369, you said you removed the carbs and cleaned hem. Did you install carb kits of simple spray some carb cleaner through them? If you didn't install new carb rebuild kits, there could be issues with blocked passages in either the low speed circuit or high speed circuit or even both. I would disassembly the carbs completely, soak them in some carb cleaner and then use compressed air to verify all passages are clean and clear. And install new needles an seats. I had a carb that the seat would not seal the fuel level and it was problems for a long time 'til I replace the seat. Also verify the floats are not fuel soaked or have any holes in them. If your spark is good and the compression like you posted, it has to be the fuel delivery problem. JMHO

 

[racerone]

The compression numbers are not engouraging.------I suspect piston / ring / cylinder wall problems !

 

[boobie]

Do a good de-carb on it and maybe the compression #'s will improve.

 

[fireman57]

The rule of thumb is that your compression numbers should be within 10% of each other. They are probably fine but make sure that when you said you rebuilt the carbs that you actually did. Not just spray cleaner in them. If your float is actually working when the carbs are off shine a flashlight in behind them and make sure you didn't suck a bolt from the carb cover back in them.