74-johnson 25 hp----problem

[ranger188]

this motor will start up fine ---first time it cranked up and was running fine for about close to five minutes than started popping and sprutting through exhaust--surging like crazy---cut it off started back up would never stop what it was last doing-----waited couple of minutes started back up started doing the same thing for about minute or two than all of a sudden stopped ran fine----it will do this in different sequences-------points reset at 20-----new water pump----new oem plugs-----carb was rebuilt last year and never ran until i put it on here today---new thermostat----compression is 120 on each cylinder-----adjusting makes no difference as to stop what its doing------what could this be---please help

 

[F_R]

So, when the flywheel was removed and reinstalled, was it done correctly? Were the shaft and flywheel tapers clean and dry? Was a torque wrench used to tighten the nut to 40-45 foot pounds? Failure to heed will result in a sheared flywheel key and throw the magnets/points timing off. And probably damage the flywheel and shaft.

 

[ranger188]

checked that looks fine--and was tighten correctly----

 

[Whaler672]

Make sure your fuel is fresh, tank is clean ( no water) and the connections are tight. Maybe sucking air.

 

[oldboat1]

Take off the flywheel and check for movement in relation to the key, and a jammed or broken key -- also check underneath for wires hitting the flywheel (frayed wiring). Check magnets for any damage. (Dangle a small screwdriver to make sure they are still strong.) Then clean the shaft on reassembly like F_R describes, and torque to spec.

Alternatively, you may have an air leak in a fuel hose -- would look for cracks at any of the nipples. It's kind of a dilemma if the hoses are old, because you have to mess with them a little to see if they are complete and flexible -- at which point they can break. But a hose leak could give you that wonky operation.

 

[Guest]

Also, unscrew the knurled screw on the fuel pump, remove the plastic cover and check the rubber diaphragm behind the fuel screen, if its torn, you could be pulling air through there.

My '73 Johnson 25 had a cracked (plastic) fuel pump cover and it pulled air though it giving it wonky operation.

 

[ranger188]

Should I see air bubbles in fuel line--got clear type line on it and see a lot of air bubbles in it---a lot ---than there will be clear spot no gas than gas and a lot of bubbles---its like this off and on----

 

[racerone]

Are they air bubbles or simply gasoline vapour due to the lower pressures ( vacuum ) pulled by the pump ??----Run with a timing light and see how spark behaves on this motor.

 

[ranger188]

could be vapor--hard to tell--that's my next thing iam going to replace coils and all points and condensors what does anyone think

 

[racerone]

Testing is the path forward.---Does spark jump a gap of 5/16" or more , yes or no ?

 

[lindy46]

Sounds more like a fuel problem rather than an electrical problem. Do you have good spark on both plugs?

 

[ranger188]

I have a video and u can tell exactly whats going on--I cant upload it on here for some reason

 

[ranger188]

Problem fixed----one coil under flywheel was cutting out----runs great thanks for all the help