1982 70 hp johnson pwr loss when warm

[ferrans]

starts good. Looses pwr when warm or heavy load. Cant run over 4200 rpm or it fails sooner. Plugs are wet when checked, and eventually foul. Plugs and coils new. 132psi compression in all 3 cyl.

 

[ob]

Re: 1982 70 hp johnson pwr loss when warm

How does it fail?Does it just cut off? If so,does it start right back up?Need some more info to determine whether we may be chasing a fuel related or an ignition related issue.Will the fuel primer bulb pump up and get completely firm?If yes ,we know that the float needles are seating good.Does the fuel primer bulb colapse or get soft when running?May have pickup tube restriction in fuel tank.Make sure the tank is venting.Before engine falls off or dies ,can you bump the fuel primer switch and get it to piuckup?This would denote a fuel restricted carburetor/s.If you pump the primer ball before engine falls ,will it pickup?This would lead us toward a failing fuel pump or air leaks.All that good?Check for good spark on all three.Will the plug leads jump a 7/16" gap to ground at cranking speed?If yes,run engine on hose and add some artificial heat(hair dryer) to powerpack and see if engine cuts out or stalls.May be a failing pack when engine gets warm.<br /><br />Well you get the picture.Post back with your findings.

 

[ferrans]

Re: 1982 70 hp johnson pwr loss when warm

Originally posted by ob:<br /> How does it fail?Does it just cut off? If so,does it start right back up?Need some more info to determine whether we may be chasing a fuel related or an ignition related issue.Will the fuel primer bulb pump up and get completely firm?If yes ,we know that the float needles are seating good.Does the fuel primer bulb colapse or get soft when running?May have pickup tube restriction in fuel tank.Make sure the tank is venting.Before engine falls off or dies ,can you bump the fuel primer switch and get it to piuckup?This would denote a fuel restricted carburetor/s.If you pump the primer ball before engine falls ,will it pickup?This would lead us toward a failing fuel pump or air leaks.All that good?Check for good spark on all three.Will the plug leads jump a 7/16" gap to ground at cranking speed?If yes,run engine on hose and add some artificial heat(hair dryer) to powerpack and see if engine cuts out or stalls.May be a failing pack when engine gets warm.<br /><br />Well you get the picture.Post back with your findings.

 

[ferrans]

Re: 1982 70 hp johnson pwr loss when warm

thanks for input. Engine falls way off, but never stalls. If I check plugs, they are very wet (all 3). Tried changing plugs right away, but it didnt change symptoms. Let it sit for hours, or overnight, and it starts and runs ok untill warm or heavy load then same thing. Primer bulb not real firm, but no change if I pump it. If I give it choke, it almost stalls. Today I will check spark, and heat up power pack and let you know.