Poor Idle. Great Mid-WOT

'96 Johnson 70hp. great compression: 122 all, great blue spark. Bought this motor on Boat #1 which i will sell, wanted to put this motor on my bow-rider Boat#2.

On boat #1: Used to run the best in idle and low speed trolling, no shutting off at all! but with no luck in mid-WOT, would always die. rebuilt all carbs and this fixed my no-WOT problem, ran like a champ with no sputters or problems. The low speed trolling went bad after the carb rebuild. Yet it always idled in neutral in the water good, never shut off until i turned the key.

At this point i swapped this motor to boat #2. On hose: Neutral idle is fantastic and steady, in gear it will run for ever, turn key off and on (back to back), cranks right up over and over (with no choking). In water: It will not idle in neutral for more than 10 seconds unless i use the neutral throttle lever to keep it at adequate rpms. When i go into gear it winds down so low that it shuts off (not really a fuel bogging sound, more like a feeling that my throttle is not advancing fast enough). I checked carb butterflys as i pushed throttle forward and they do advance smoothly as i push. Okay so I then have to choke-start it to crank up, it just refuses to crank regularly, but it cranks every time. Takes me about 3 short bursts forward in gear to get it finally get it to reach, slowly but surely, into mid-high throttle, after that it will go all day no problem, full of power and no overheating. After warmed up, same issues. Trolling seems to be weak, if i slow too much like if the boat sitting all the way in the water, it will try to die. I really want to ski and this is making my life of skiing very difficult!!!!!:mad-new:

Note: During the swap i had to disconnect all linkage and cable as typical. i stupidly reinstalled the throttle and gear shifter cables backwards:facepalm:, cranked it and immediatley shut off the engine as it begin to roar up rpms in gear (didnt get any higher than 2000 though), swapped them back.

A few things: Idle air screws are set at 1.5 turns out. Throttle arm with plastic piece that has a pointer is lined up to carb linkage. Should this pointer thing be pushing carb linkage a bit forward at all times? Mine seems to be sitting against the linkage but not affecting it until throttle engagement. I will post pics later...Thanks to any and all advice here guys!

-Tripp

Re: Poor Neutral Idle and Troll, great Mid-WOT?????

Re: Poor Neutral Idle and Troll, great Mid-WOT?????

Have you adjusted the low speed needles while the engine is in the water?

Re: Poor Neutral Idle and Troll, great Mid-WOT?????

Re: Poor Neutral Idle and Troll, great Mid-WOT?????

I have but its very difficult to troubleshoot this way because i need someone else who has to use the neutral throttle lever to keep it from dying. I will try this again though. The flat head screws with the springs are the low speed needles, right? Here's some pics:

Re: Poor Neutral Idle and Troll, great Mid-WOT?????

Re: Poor Neutral Idle and Troll, great Mid-WOT?????

Here are a couple more. Sorry if they are blurry, had to reduce size in order to upload

Re: Poor Idle. Great Mid-WOT

Ok trip I think i know whats wrong here.
your engine is advancing too late !!!!!!!!!!
your not advancing until engine is doing about 2250 rpm then it goes well with plenty of oomph ?

your cable is set wrong, the main lever in the last pic shows the spring is too far compressed, this means the screw for the idle needs to be turned in a few turns.

Now before you move the idle screw at the bottom of the main lever, take off the rod between main lever and the plastic roller plate.

Now just screw in the idle screw to relieve a bit on the spring at the top.
then connect up the rod to plastic bit with a tiny gap of 10 thou !!!!!
With engine on hose youl need to get a idle of around 900 to 950rpm as when in the water this will drop to about 750 to 800 due to back pressure.
once in the water you can always dial it back or up a touch to get it how you want it, but on hose will always be higher revs.
Now the Cables !!!!!
the throttle cable needs to be adjusted by the knurled plastic black bit on the engine end.
once you have the idle all done the cable needs to be put back with NOT TOO MUCH stress pushing/pulling the cable to idle position.
Just make sure with engine switched off that the cable puts the carbs to full throttle and then to fully back into idle.

so as you don't have to take black cover off the carbs to see full throttle, the pins on the side of carbs go straight up and
down when its full throttle position on the butterflys.

The idle screws on the carbs are in way too far, they should be out about 2 1/2 turns out, 1.5 turns is definitely too little.
these screws are what was messing me up a lot with mine, as mine were originaly 2 full turns from fully in (gently in not hard).

hope this helps a bit

I can see what is wrong as I had mine adjusted exactly the same as yours after a carb re-build and cable clean up.
I put it back like I thought would be right and buggered it right up ha ha ha



phill

Re: Poor Idle. Great Mid-WOT

okay Phill now i got something to work with!! I will move the screws to 2.5 out right away. as for the idle screw, which one is it? The one with orange grease looking stuff on it or the one below it next to the purple wire?

also when u said "Now just screw in the idle screw to relieve a bit on the spring at the top" are you referring to the spring that is directly below the flywheel in pic 2 of 3?

Re: Poor Idle. Great Mid-WOT

yes the spring I refer to is the one under the flywheel that is pushing back the main throttle arm.
that is back a touch too much at the moment.

the idle speed screw is the screw at the bottom by the purple wire that goes to the solenoid.
ive put a pic here to show the idle screw.

what is happening is your starting to open the carbs up a fair bit without the timing moving at all.


now being as the timing is what makes the idle revs go up or down with the carbs closed, we have to use the idle screw to
bring the revs up a touch.

you will have to dis-connect the rod from main lever to the plastic roller to set this up.
Make sure the carbs are kept closed all the way (rubber band to keep roller pulled back while rod is disconnected).
then screw in the idle screw to get around 900 to 950 rpm on the hose with muffs etc.
once you have this youl just have to adjust the rod so it does not exactly make the plastic plate touch the roller, tiny gap of 10 thou.

you just adjust the cable by turning the knurled bit on the cable, then keep checking it as you adjust for wot and for
bringing it all the way back to idle without any snags.
youl notice that the warm up lever is also gonna be a lot less than some folks who have it screeming when they have it set up wrong.

anyway here is a pic to show the screws etc.
note I had everything wrong in the pic below, the gap at plastic plate was fine, but my spring was too compressed and
the idle screw not touching the main lever down at the bottom, it should be touching.
once I let the lever go back a bit and adjusted the rod it all came to be good.

phill

Re: Poor Idle. Great Mid-WOT

Alright Phill i will give this a try. This makes a lot of sense! I just never have messed with timing and whatnot. Thanks again man! Ill let you know the results later. PS so what is that screw with the orange stuff on it anyways? And did you ever get your motor running right with the manual?

Re: Poor Idle. Great Mid-WOT

Okay I am trying to adjust this but the arm isn't budging easily off at the roller side. Do I disconnect at main lever side where cotter pin is?

Re: Poor Idle. Great Mid-WOT

Hasnt been much on this thread but just for the record... I adjusted the timing advancement spring to be less compressed but did not touch the idle screw as i knew i had never adjusted this before and it used to idle fine. I figured the advancement and idle air screws were the main problem, per Phills replies...and they were. It now runs like a brand new freakin motor. I skied with 4 ppl (including myself) on boat and 1 in water for 5 hours each day all weekend!!!! 0 hick ups, 0 shut offs, 0 studders or hesitations. Just perfect air/fuel/spark ratios all weekend!!! Quite less mpg than the oldy but goody 1978 55hp seahorse!!!!

I have one question though: Anyone know for sure if with most other outboards that the idle air screws are supposed to be 1.5 turns out and that it is special that this model johnson needs 2.5 turns out?

Re: Poor Idle. Great Mid-WOT

1 1/2 turns out is just a static setting to get the engine to run. You have to adjust the low speed needles with the boat in the water and in gear to properly set them. On a multiple carb engine, the engine might run better with a different adjustment on each carb.

Re: Poor Idle. Great Mid-WOT

Thanks for the info Daviet. My sweet spot was 2 3/4 turns on all 3 carbs.

Re: Poor Idle. Great Mid-WOT

Glad you got it running properly.

Re: Poor Idle. Great Mid-WOT

2 3/4 is often about right on these triples of around the same year from what ive read.

im very pleased you have had a good time with the engine tripp,

ive still to test mine, been too busy with other stuff to get out and have a blast.

tripp how much fuel would you say it uses per hour when ski-ing or an average etc.

I find mine to be a lot heavier on the juice than my old 60hp merc triple , but it might just be me noticing it more due to prices being so high in the uk ?6.50 per gallon = over $10 us money plus the 2 stroke oil as well


phill

Re: Poor Idle. Great Mid-WOT

Not sure on exact mileage but on an average day (4-5 hours) I burn about 5 gallons. we only ski maybe a full 2 hours of that. I'd say be ready with ur 6 gallon tank full and a little reserve gas in another tank!

It depends on how heavy ur load is too, I had atleat 3 ppl in at all times with dog and child. Then 5 ppl some of the time

Re: Poor Idle. Great Mid-WOT

And oh dude holy cow its 10 $ over there now? Dang man. Yea I filled up the 6 gallon for like 20 $ or more. On average about 30 $ a day plus oil with this motor