1979 johnson 75hp,bogging down

nednag

Recruit
Joined
Jan 9, 2012
Messages
1
son has this motor and when we went out saturday it ran good for a few miles and then started to act like a fouled plug,bogging and kicking in and out of full throttle.ran back to ramp at full throttle but no rpm's,ran smooth like it was hitting on all 3 cylinders but could not get any speed or rpm's.changed plugs and still could not get any rpm at full throttle!we've had a lot of extreame air temp changes here(30 for a couple of days and 60 for a couple,roller coaster weather) could this be water in the carbs caused by condensation of the ethenol gas in the tank??that's my guess!or could it be the power pack and how do you test that? any suggestions or quick fixes would be greatly appreciated.
 

Snoopy Joe

Cadet
Joined
Jan 22, 2012
Messages
22
Re: 1979 johnson 75hp,bogging down

It could be water in the fuel. When its acting up, start pulling plug wires off to see if there's a change. Be sure to use proper plug pliers.
 

Bill3434

Petty Officer 1st Class
Joined
May 29, 2011
Messages
398
Re: 1979 johnson 75hp,bogging down

son has this motor and when we went out saturday it ran good for a few miles and then started to act like a fouled plug,bogging and kicking in and out of full throttle.ran back to ramp at full throttle but no rpm's,ran smooth like it was hitting on all 3 cylinders but could not get any speed or rpm's.changed plugs and still could not get any rpm at full throttle!we've had a lot of extreame air temp changes here(30 for a couple of days and 60 for a couple,roller coaster weather) could this be water in the carbs caused by condensation of the ethenol gas in the tank??that's my guess!or could it be the power pack and how do you test that? any suggestions or quick fixes would be greatly appreciated.

You don't need ethenol gas to have a condensation problems. Up to a point ethenol would help the condensation since water will mix with alcohol but not the the gas; but alcohol also absorbs water freely. Did you have a lot of humidty in the air? Warm dry air then cold dry air shouldn't cause any issues; warm humid air when cooled will equal lots of condensation. If you suspect water, change out the fuel and see what happens. If it doesn't solve your problem then probably not bad fuel, that's why I didn't say throw out the fuel. Thought I had a fuel problem gave it away for it only not to be the problem.
 

jjacobs007

Lieutenant
Joined
Mar 10, 2009
Messages
1,257
Re: 1979 johnson 75hp,bogging down

if gas is good,start at fuel tank and work your way to cylinders.check everything
 
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