1979 evinrude 140. idle problems. timing? help please

[dom_litty09]

i have a 1979 evinrude 140hp V4. i recently rebuilt 2 cylinders (due to pre-ignition 2 of the pistons were shot) rebuilt the carbs. all new fuel hoses from fuel pump to carbs. and it still seems to not be running right.. the timing/idle screw is all the way out (pic below) and the boat is only idling at about 800 on the muffs. so when its in the water it idles even lower and doesnt stay running. which in my opinion it shouldnt have to be out that far.. when i first got the boat it was only about half way out.. not sure if it matters or not but the base gasket had a small crack in it when we put the powerhead back on. other than that i dont know what the problem would be.. is there some other way to adjust the idle without using the timing screw? any input would be great. thanks.

 

[metriccrescentwrench]

Re: 1979 evinrude 140. idle problems. timing? help please

What's the timing at idle? It should be about 4 - 6 degrees before TDC (I'm looking at a 1981 factory service manual, I'm assuming yours should be the same).

Also, make sure that all carb butterflies are totally shut at idle (idle speed is adjusted by varying the timing), the only air getting through at idle is through the small air metering holes in the throttle plate.

 

[dom_litty09]

Re: 1979 evinrude 140. idle problems. timing? help please

i am not sure what the timing is at idle.. i dont have a timing light.. and im almost positive all the butterflies are closed.. i can check to make sure tho

 

[boobie]

Re: 1979 evinrude 140. idle problems. timing? help please

Some parts houses will rent you a timing light or maybe try Harbor Freight. You'll need a timing light to do the job properly so you don't blow your mtr.

 

[emdsapmgr]

Re: 1979 evinrude 140. idle problems. timing? help please

Agree, the idle screw seems to be adjusted all the way in. That's not normal. The idle is set by adjusting the idle timing, not by any carb adjustment. You must set the idle (by adjusting that screw on the spark advance lever) when the boat is floating normally in the lake. The engine must be idling in forward gear. Set the idle between 650 and 750 rpm's. You can't set it on the trailer. The actual degrees of idle timing is not really important, you want the idle to be at the correct rpm's. It is handy to set the idle timing by degrees, then make your final adjustents in the lake. Are you sure the engine is running on all 4 cyls? You can check for spark when the engine is idling on the trailer. Pull one spark plug wire off one spark plug with a set of insulated pliers. The engine rpm's should decrease. Replace that plugwire and pull another plug wire off. If you pull one plug wire off, and the rpm's don't decrease slightly, that plug may not be firing.

 

[dom_litty09]

Re: 1979 evinrude 140. idle problems. timing? help please

ok. ill check it out later today. might swing by auto zone and grab a timing light also. ill post later. thanks

 

[dom_litty09]

Re: 1979 evinrude 140. idle problems. timing? help please

i just went out to check the motor. i think it might be too cold here for it. the trim doesnt want to work now.. so hoping for a warmer day so i can test spark and what not. if it doesnt warm up then this might just be a project for next year.. ill let you guys know. thanks for the input so far

 

[emdsapmgr]

Re: 1979 evinrude 140. idle problems. timing? help please

That 79 trim system is has a separate electrical system from that of the engine-unlike the newer models. It has it's own main cables that go direct to the battery. Since that system is separate, it also has it's own fuse in the trim electrical box. Make sure that fuse is not blown.

 

[dom_litty09]

Re: 1979 evinrude 140. idle problems. timing? help please

just went out and messed with the boat a lil bit. it was the trim fuse. also, figured out that cyl #1 isnt firing.. i could actually take the plug wire off the plug without plyers on that cyl. so no spark. where would i go from here?

 

[emdsapmgr]

Re: 1979 evinrude 140. idle problems. timing? help please

That year's engine had identical twin power packs. One for each head. Swap them out. If the no spark problem moves from head to the other, likely the power pack is bad.

 

[dom_litty09]

Re: 1979 evinrude 140. idle problems. timing? help please

i swapped the power packs around today. the no spark problem moved to the other side. so i am guessing the power pack is bad. gonna call around and get some pricing then go from there. hopefully it works out

 

[dom_litty09]

Re: 1979 evinrude 140. idle problems. timing? help please

ok. so i put on the power pack today. all cylinders are now getting spark. but it is still running about the same.. where would i go from here? could it be that the base gasket was cracked a little bit? im not really sure what else