1975 johnson 70 hp does not rev more than 3200rpm

[tacomaguy]

Hi,here is a litle review of this OB,The problem start arter ran out of fuel,Things i have done on it because was sit for over 3 years,carbs,new hoses,plugs,head gasket and surface,exhaust gasket,intake gasket to check reeds they wore fine.w pump,fuel line ,new tank and fitting.Okay, compresion #1 139,#2 140.#3 139,spark thunder blue over 7/16.Idle kind of rougt at 1000 rpm but at high rpm very smooth no puff or backfires.

 

[Cricket Too]

Re: 1975 johnson 70 hp does not rev more than 3200rpm

Welcome aboard tacoma, did you do a link and synch after you rebuilt the carbs and re-installed them?

 

[tacomaguy]

Re: 1975 johnson 70 hp does not rev more than 3200rpm

Yes, I did ,I followed the manual inst..0 tdc at idle roller on bottom cam mark.When i got the ob it did not even start. So, i did the carb i could not get the fixed jets out so, i clean them really good.I don't think it is something related with them because the motor was running good before it ran out of fuel. I opened the fuel pump and the diafragma felt hard. I'm not sure if it is normal or not. The ob started right up. I checked the plugs they looked even.

 

[tacomaguy]

Re: 1975 johnson 70 hp does not rev more than 3200rpm

Up date.I worked on my ob this weekend,i cheked fuel pressure about 3 psi at idle[900 rpm] and increase when i rev it up,I disconeted the black and yellow wire to discrad control bor no change at all.I took carb a part this afternoon hopping find something not in order.This is one of those problemsthat drive you a litle cucu.Thanks for your help.

 

[tacomaguy]

Re: 1975 johnson 70 hp does not rev more than 3200rpm

Yesterday i took the carb just to make sure nothing wong whith them,They look in working order,no bloked pasagesor or orfices.This afternoom i'm going to take the flywheel out ,i forgot the 3 coils are new.I'll let you know what i found,small tip when i put my hand over the upper splug i fell current drop?

 

[tashasdaddy]

Re: 1975 johnson 70 hp does not rev more than 3200rpm

powerpack?

 

[tacomaguy]

Re: 1975 johnson 70 hp does not rev more than 3200rpm

Here we go again.this weekend i took the flywhell to inspect under it and stator and timer looked in very good for this age.i clean the sensors,stator and i used very fine sandpaper and elect part cleaner to clean the flywheel i noticed some kind of scratches on the stator and flywheel not a big deal becouse when i did the exhuast gasket i had some broken botl and i had to dril them to take them out.Okay ,i spray some mix in the carb and no change at all,i did all this at home on muffs.i read about how to check thi power in another topic,i heated the ppack and i noticed a very small change to worst,i'm going to follow your opinion tashasdaddy.

 

[tashasdaddy]

Re: 1975 johnson 70 hp does not rev more than 3200rpm

hope i'm right. good luck.

 

[tacomaguy]

Re: 1975 johnson 70 hp does not rev more than 3200rpm

Hey, bigdaady ques what.i think narrow the spot,i hooked tlight and cyl 1 has black spot at hihg rpm so, i swaped coil 1 to 2 and i got same result.Cyl #1 is missing spark at high rpm.well i fell more confidence to replace the power pack.I'll let you now the result.Thanks.