Johnson 70HP Unknown problem

[macsub]

Hi guys, I'd like to ask about a little problem I'm having with my Johnson 70 HP, year 2000.
It happened one day after not being used for about 20 days, all day without any trouble was that it failed on our way out, would't hold for long after starting (which happened because this motor has a valve you move manually, injecting gas to each carburator instead of a choke, making starting easy) and when geared into forward, it stopped. We didn't even go 100 ft away so we swam back to shore.
When checking my manual, and after following fuel lines, everything seemed ok so I unassembled the carburators finding no gas in two of them, top and middle, only the third (bottom) had gas on it so I found the problem to be that the inlet needlevalve was stuck to the seat, this is what the buoy opens and closes when gas reaches its limit, but in this case there was no gas coming in, dry. I thought it wouldn't cause any more problems but last time we had to move the gas primer to get started but had to accelerate suddenly to get combustion, then let it drop and finally before it stopped, gear forward and keep accelerating up and down till it got some speed, then it wouldn't fail.
I also moved the idle mixture valve from 4.5 turns to 2.5 as the manual says. Any idea of what's wrong? I hope my cylinders aren't screwed for not having gas in the top 2 cylinders.
Thanks in advance for your time.
M.

 

[jtexas]

Re: Johnson 70HP Unknown problem

welcome to iboats!

When you found that your float valves were stuck shut, did you rebuild your carburetors?

When you pump the primer bulb, does it get firm and stay firm?

Have you given any thought to repairing the electric primer solenoid, so you can operate it from the keyswitch?

 

[macsub]

Re: Johnson 70HP Unknown problem

Hi jtexas, thanks for taking the time.
Here are my answers:
-What do you mean "rebuild carburetor"? I dont think I did that, but I guess thats what I should do.
I just cleaned it but now I think I did not clean properly, because the problem looks similar but a little better than before.
-When I pump the primer bulb, yes it does it get firm and stays firm.
-I didnt know I could operate the primer solenoid from the key switch, that sounds very good, I will check into that. Is it the same as the manual primer with the little red handle located by the front-right side?

I will clean carburators neddle and seats deeply and see what happens.
Thanks,
M.

 

[tashasdaddy]

Re: Johnson 70HP Unknown problem

you have 3 carbs, the center on is different, mark it for center. also don't mix the parts of the carbs up, keep them separate.
http://forums.iboats.com/showthread.php?t=244013


the red handle on the primer has to be inline back over the body of the primer solenoid, to work with the key. any other postion, it is going to allow fuel into the intake, and flood the motor.

 

[F_R]

Re: Johnson 70HP Unknown problem

Nobody ever told you to push in and hold the key while turning it to crank the motor?

Didn't those inlet needles have little wire clips to drag them off the seat?

 

[macsub]

Re: Johnson 70HP Unknown problem

My manual asks to move the red switch when the motor is cold.
I'll try to use the key though.
I cleaned the carbs thoroughly and everything seems new, the inlet needle valve with red tip looks new, I haven't replaced anything yet.
The only thing I've moved is the idle mixture needle valve which had 4.5 turns previousely and now 2.75 turns from tightly closed as the manual requires.
On the last trip, we had lots of problems starting and getting into gear without it dieing. I had to accelrate all the way and gearing at high relolutions which is very bad.
Is there anything else on the carbs to adjust besides the idle mixture needle valve?

 

[jtexas]

Re: Johnson 70HP Unknown problem

Do you see your red lever in this picture?

Does your keyswitch have a "push-to-choke" feature?

If so, I think we can get your electric primer working.

try this procedure for setting your needle valves
http://forums.iboats.com/showthread.php?t=167352

 

[macsub]

Re: Johnson 70HP Unknown problem

Thanks JTEXAs,
I've cleaned and reinstalled carbs, screwing the idle mixture needle valve 1.5 turns from completely closed.
The motor's gas pump was primed and key's choke, which is working fine, pressed in, starting the motor but it wouldn't hold for long. Smoke and idling very low and seemed restricted, not developing a stong smooth combustion but a poor one.
What could I've done wrong?
Afterwards, I tried starting out with 4.5 turns like it was set originally, before the inlet needle valve got stuck, it would try to start strong but never really got started, died out immediately.

 

[jtexas]

Re: Johnson 70HP Unknown problem

ok, try it one more time, but this time, instead of just setting the mixture valves and leaving them alone, try adjusting them while the engine is running, like this:

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

 

[macsub]

Re: Johnson 70HP Unknown problem

So let me ask, to be certain that the S/S needle valve you mention is the same as the idle mixture needle valve as called in the book. Allow me to piont it out, in the picture above it would be the screw with spring to the right of the word BASE, in green, at the top of the picture.
So I'll turn this valve 1 1/2 turns out, away from each carburator, prime, choke and start motor, accellerating enogh for it not to die, 600 - 800 rpm ? Then, turn valve inward 1/8 turn each time to encrease accelaration, giving the motor some time to resincronize, until motor backfires or missfires.
The perfect setting will be found in the 1/4 turn out range.
Won't I need to accellerate any more?
Isn't this accellerated setting going to drop when I lower the accellerator down?
I'll try again and see, but the first time it died before I could turn 1/8 in.

 

[tashasdaddy]

Re: Johnson 70HP Unknown problem

i am not sure, but i don't think these are the correct procedures for a 2000 70, they were for older motors. i read in a manual, i no longer have, that these were set at the factory. and there were other directions to reset them if they had been tampered with. see if you can find a OEM manual for your particular motor.

 

[jtexas]

Re: Johnson 70HP Unknown problem

ok, sorry, I must have misunderstood your previous description - yup that's the screws I'm talkin bout.

in this case, I have to yield to tasha's experience, and hope I didn't steer ya wrong - or at least not too far wrong.

 

[macsub]

Re: Johnson 70HP Unknown problem

In my manual there are only instructions for years 1995 to 1998 being the manual for 1995 to 2003, 2 to 70 hp by CLYMER.
Let me know if you find out something, thanks guys.

 

[jtexas]

Re: Johnson 70HP Unknown problem

ok, that's clymer for ya.

I have both seloc and the factory manual, and get some good tips from seloc but really rely on the factory manual. Highly recommend it. For those little details that vary from year to year.