High idle

[Steveng]

I have a high idle (1500 rpm) after a rebuild of my 91 70hp Johnson outboard. I rebuilt the power head with all new components, rebuilt the carbs, and pressure tested the case. It held 8 lbs for over several hours. I was happy until I placed it back on the motor housing and started it for the first time. The engine runs very well except the idle will not go below 1500 rpm. The idle screw is completely backed off and the throttle cable is not holding the carbs off idle. The engine settings were set after the first rebuild, but there was a case leak. I split the case and resealed it and now after the pressure test (as stated no more leaks), the idle will not go below 1500, even with the carbs completed closed. Any suggestions?

 

[steelespike]

Re: High idle

I would suspect some sort of air leak you could use a piece of hose like a stethescope
to listen for a leak.or carefull spray some wd40 or some inert fluid in suspected areas
see if any change.You might double check the timing.

 

[Steveng]

Re: High idle

Air leak? Are you talking around the case or where? I am positive the case is tight, because of the pressure test. Would the timing change after the case was resealed?

 

[dehydrated]

Re: High idle

air leak around the carb bodys and hoses would cause high idle

 

[Steveng]

Re: High idle

I sprayed wd 40 around carbs, case and fuel lines, no reaction at all. Checked timing and it is dead on the mark. Help, i'm lost!!