adjust idle on old 1978 johnson?

[Tripp Halbert]

1978 55hp johnson here. rebuilt powerhead. good compression and spark. clean carbs, new plugs and coils. completely rewired.

Have had it for 2 years and it always has got me from point a to point b, no problem. The idle has always been unpredictable though i.e. stalls when getting close to the dock, sputters to a stall at to low of rpms in neutral as well as in gear. It will not stay running in neutral unless you play with the throttle at all times. it seems to run the best and idle better when u have run it all day though.

problem: I see no idle air screw with a spring on these carbs? how the heck can i get this thing running more smoothly?

 

[Tripp Halbert]

Re: adjust idle on old 1978 johnson?

also: what other years/hp's will be a compatible with this engines control box?

 

[Fleetwin]

Re: adjust idle on old 1978 johnson?

If it's been two years, your carb's are probably gunked up again. Today's fuels will not tolerate sitting around in an open system, such as a carburetor.

With that said, I think your '78' still had idle adjustment screws. They would be on the lower portion of the carb's, on the front side. You may be, or not, be to access them with the air silencer on.

The best way to start is to turn them GENTLY all the way in and turn out 1 1/2 turns. Adjust from there with a warm engine.

 

[Tripp Halbert]

Re: adjust idle on old 1978 johnson?

no no, the motor has been run on my boat for the last two years, it hasn't sat much at all. But i did not know about those screws, i will give that a try, thank you!

 

[boobie]

Re: adjust idle on old 1978 johnson?

If in fact it's a '78 55, they had fixed low speed jets. Post a model #. No adjustment needles.

 

[Tripp Halbert]

Re: adjust idle on old 1978 johnson?

55el78s

 

[tomhath]

Re: adjust idle on old 1978 johnson?

What does "clean carbs" mean? You took them completely apart and cleaned everything, including the idle circuits? Or when you bought it the seller said he'd cleaned them? It sounds like either the carbs were not quite cleaned or the throttle/ignition linkage might be off.

 

[Tripp Halbert]

Re: adjust idle on old 1978 johnson?

yes carbs were taken apart and cleaned by myself. I am thinking the linkage is off as you say. Almost seems like the spark advancement doesnt engage quick enough to sync in with the carbs opening. not sure though. here is the cabrs, i will post some linkage pics later.

 

[boobie]

Re: adjust idle on old 1978 johnson?

Edit......

 

[boobie]

Re: adjust idle on old 1978 johnson?

What exactly is the compression on it ??

 

[Tripp Halbert]

Re: adjust idle on old 1978 johnson?

compression is probably great on the 55, we skied with this thing all summer w/ no problems. honestly, when we were running it all day is when it idled perfectly and performed best. i will run a comp test tonight and post results, i am curious.

The reason i think it is a carb issue is because my 70 did the same thing, rough take offs and stalling slow downs, perfect performance at mid-high rpms, poor idle and death in neutral idle. I finally discovered the 1996 models carb turn out was supposed to be 3 1/2 turns out, not the normal 1 1/2 turns out, which made my 70 2stroke run like a 4 stroke, so smooth and quiet. it has not stalled on me once since this tuning, NOT ONCE, and runs strong.