1975 70hp Evinrude has no vacume in cylinder

[timayres]

Re: 1975 70hp Evinrude has no vacume in cylinder

I have another older motor that has the same carbs. I have tried one of these but had the same problem. Then I rebuilt it and there was no change. Then sprayed fuel in carb and no change. If I remove the high speed jet plug gas runs from the carb. While the engine is idleing I can cover the top carb and it makes no difference. The other two carbs react very quickly if I cover them.

 

[The Marine Doctor]

Re: 1975 70hp Evinrude has no vacume in cylinder

When you completely cover the top carb with your hand...does it flood over with fuel?<br /><br />TMD

 

[timayres]

Re: 1975 70hp Evinrude has no vacume in cylinder

Yes

 

[The Marine Doctor]

Re: 1975 70hp Evinrude has no vacume in cylinder

We then can conclude that there is vaccuum in that cyl.<br /><br />What kind of spark plugs are you using?<br /><br />Surface gap or conventional plugs?<br /><br />I wonder if maybe the throttle plates are not aligned properly?<br /><br />TMD

 

[rickdb1boat]

Re: 1975 70hp Evinrude has no vacume in cylinder

I believe OB hit it on the head. Did you ever look into the throat of the suspect Carb. and see if the flap is opening up smoothly when throttle is applied? Stranger things have happened.

 

[timayres]

Re: 1975 70hp Evinrude has no vacume in cylinder

NGK conventional plugs. Your reference to throttle plate alignment opened my eyes. If you are refering to synchronizing the linkage between the carbs, I forgot to do that!! I'll try it tonight.<br />Thanks!