Idle on an 1965 Evinrude 18hp

[joelmash]

Have trouble getting my 18hp to idle. If i give it gas i can keep it running. when i drop back to idle it wants to die. I have rebuilt the carb, new fuel pump, new plugs, coils, points, set the points and set the low idle screw to 1-1/2 turns out. it also seems to occasionally blow back out in the exhaust. Any ideas

 

[racerone]

Sounds like classic ---lean sneeze--- on this motor.---open low speed mixture screw 1/8th turn at a time and test.----or throttle plate is not closed /opening too soon at idle.----And post the compression values on this motor.

 

[Crosbyman]

if carb adjustement don't work ,compression is OK , ignition etc... make certain the narrow side channel sending fuel up to the top idle cct chamber under the dome plug is 100% clear otherwise the idle fuel supply will not flow up the side , drip down and get sucked in the engine.

see older carb diagram idle path... and 18hp carb showing side channel

 

[Crosbyman]

your 18hp comes from a long family of oldies and this books can supply you with valuable info... nothing new under the sun !
just download store print locally

https://www.socalaomci.com/library/johnson_service_manual_10th_edition.pdf[/URL
timing video

 

[jimmbo]

You set the Idle Mix Screw 1 1/2 turns out. That is an initial Set Point, usually quite Rich, but will allow the motor to start Have you tried adjusting it since?

 

[racerone]

These 22 cube motors like yours are some of the best they made over many years.----In good condition they idle very well.----So nice that you don't want to stop it.

 

[jimmbo]

The production run was from the mid 50s till about 1980