nick_bassboat
New member
Dear users,
On my boat i have a 1976 70753E 70hp Evinrude,
it runs under load, better at high rpm but doesnt idle very well. (i cant get it to idle low enough because it'll stall).
The rpm is quite steady but has occasional dips which cause the engine to stall when too little throttle is applied. for example ill adjust the throttle to get an average of 2k rpm and without touchinganything the rpm wimm fluctuate between approx 1.6k and 2.4k. At higher Rpm's these dips in rpm still occur . the dips occur regardless of the amount of choke applied and regardless of if the motor is hot or cold. the dips occur regardless of if the motor is in gear or not(we are using a test tank with a normal prop).
what ive tried to fix it:
-cleaned carburaturs (removed the jets and the brass part where the gad entired the float bowl). cleaned everything with carb cleaner. using a toothbrush to clean the bowls(they looked quite good before cleaning)
-replaced spark plugs
-checked compression(135psi on 2 of the cylinders, 140psi on the 3rd;
evinrude manual said it should be 150psi)
-visually checked ignition coil wires going to the spark plugs(they look very good, no cracks in insulation)
-replaced all fuel hoses
-checked fuel pump (pumps good;to 1.6m height using the dtqrter motor to turn the engine).
the engine appears to turn quite easily with spark plugs removed turning it by hand via the flywheel. theres some resistance but thats quite definitely the impeller that i feel.
it had new clean fuel.
i noticed the screw under the flywheel for adjusting the timing was not in its original position. it should be turned out half an inch and currently that measurement is 3/4 inch.
the ignition coil had some cracks in the insulation but i replacef one of them with new and wrapped 1mm plastic around the other two and filled the cracks in the indulation with silicone so i dont think those are causing the issue.
my last guesses are that the timing is incorrectly adjusted or that its grabbing 'false air' either behind the carbs(gaskets appeared to be in good condition) or perhaps through some other seals/gaskets.
i could use dome advice, i think i checked the most common things and unfortunately have not been able to figure it out.
thank you very much!
On my boat i have a 1976 70753E 70hp Evinrude,
it runs under load, better at high rpm but doesnt idle very well. (i cant get it to idle low enough because it'll stall).
The rpm is quite steady but has occasional dips which cause the engine to stall when too little throttle is applied. for example ill adjust the throttle to get an average of 2k rpm and without touchinganything the rpm wimm fluctuate between approx 1.6k and 2.4k. At higher Rpm's these dips in rpm still occur . the dips occur regardless of the amount of choke applied and regardless of if the motor is hot or cold. the dips occur regardless of if the motor is in gear or not(we are using a test tank with a normal prop).
what ive tried to fix it:
-cleaned carburaturs (removed the jets and the brass part where the gad entired the float bowl). cleaned everything with carb cleaner. using a toothbrush to clean the bowls(they looked quite good before cleaning)
-replaced spark plugs
-checked compression(135psi on 2 of the cylinders, 140psi on the 3rd;
evinrude manual said it should be 150psi)
-visually checked ignition coil wires going to the spark plugs(they look very good, no cracks in insulation)
-replaced all fuel hoses
-checked fuel pump (pumps good;to 1.6m height using the dtqrter motor to turn the engine).
the engine appears to turn quite easily with spark plugs removed turning it by hand via the flywheel. theres some resistance but thats quite definitely the impeller that i feel.
it had new clean fuel.
i noticed the screw under the flywheel for adjusting the timing was not in its original position. it should be turned out half an inch and currently that measurement is 3/4 inch.
the ignition coil had some cracks in the insulation but i replacef one of them with new and wrapped 1mm plastic around the other two and filled the cracks in the indulation with silicone so i dont think those are causing the issue.
my last guesses are that the timing is incorrectly adjusted or that its grabbing 'false air' either behind the carbs(gaskets appeared to be in good condition) or perhaps through some other seals/gaskets.
i could use dome advice, i think i checked the most common things and unfortunately have not been able to figure it out.
thank you very much!