Logo
FULL SITE MENU

Johnson 115 missingback fires

R

roger_w

New member
"have replaced all coils,plugs

"have replaced all coils,plugs,fuel diaphram,rebuilt carbs,compression is 120 all cyl.checked all reed valves.acts like its sucking in air from somewhere,could this be crank seals?"
 
not sure the model# its a 1978

not sure the model# its a 1978 model.sounds like its backfiring out the exhaust.the timing is right on.
 
"i would pull the flywheel,and

"i would pull the flywheel,and ck for sheared key,regardless,what u see the timing at...also,maybe before u do that,..ck the coil wiring,...sucking air,..is not gonna make it backfire like that.."
 
agree...and if a plug wire is

agree...and if a plug wire is crossed and its been played with any length of time the the pin is sheared on that model motor..been there and done that.
 
pin is ok and wires are not cr

pin is ok and wires are not crossed.will only start with choke on and will only run with the choke on half way.thats what makes me think its a vacume leak.
when at idle seems like it only runs on 3 cyl.
 
"First of all get it in a barr

"First of all get it in a barrel or at sea, no muffs!
Pull the carbs again and double check float levels and that ALL channels are open. Install with new gaskets and no sealer!
Then do a complete synch according to the manual for Your engine. At the same time have a timing light at hand so You may check not only that You have spark on all cyl's, but that there is no double firing (2 cyls fire at same time) going on."
 
"Morten - This sounds like wha

"Morten - This sounds like what I went through with my 79' 115 Evinrude. It had a lot of stumbling, back-firing, and ran best when I was heavy into the choke. Of course my problem turned out to be no pressure in the lower end due to stuck rings, and a leak at the crankcase assy halves. Without lowend pressure the air/fuel mixture can't make it's way to the top which is why I was always into the choke. My leak was finally discovered when I had a friend turn the engine over while I observed. As it turned out it was a blessing in disguise because the stuck rings would've lead to a complete burndown had I forced the situation...all parts (except gaskets/seals)are still useable."
 
"thanks guys,iput it in a barr

"thanks guys,iput it in a barrel,cranked it up,runs irratic and pops about every 15 seconds or so.checked plug wires and fireing,all good,i think its more a problem like Davids.looks like i may have to tear it down."
 
"The main reason I wanted it i

"The main reason I wanted it in a barrel or at sea was to have the back-pressure correct. That way one might eliminate the lean-burning symptoms caused by no back-pressure. What is 'left' one has to start chasing. An engine of this age is probably due for a complete re-seal, but first please check that thermostats work properly, and that the engine reaches an even temp on both banks - close to 'too hot to touch'."
 
"Befor you do a tear down pull

"Befor you do a tear down pull your fly wheel again,and check the magnets. Make sure none has slipped."
 
"Roger - Be sure to verify the

"Roger - Be sure to verify the carburetor butterflys completely shut when at idle. This turned out to be my final issue with my setup. Unless the flys are completely closed you'll lack the vacuum necessary to pull enough fuel out of the orifices and it will turn into a lean idle condition causing many of the symptoms you've described. This is part of the carb synchronization that needs to be done and I missed it early on. By the way, my engine still needed a rebuild and I've since completed that task."
 
Back
Top