1989 johnson 70hp fires for a second

[skeeter69]

Hello my first time posting anything.also my grammer is terrible ok that said i need help.i have a johnson 70hp w/vor pump.it was running on earmuffs last fall at a good idle.Then it stoped ,it will fire on all cylinders,get good gas to all carbs.it fires for a second shakes really hard left to right backfires and thats it.opened the bottom of all carbs great gas mixed came out even tried a remote tank. is there any thingi should be looking for electrically.even spraying gas in each carb does the same thing everytime.

 

[tashasdaddy]

Re: 1989 johnson 70hp fires for a second

sounds like you have broken the key in the flywheel, and crankshaft. this throws everything out of time.

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

I thought it might have something to do with that.i'll pull the flywheel and check for sheared key. as far as the crankshaft key where is that?i would love to not have to take this to the local shop as i know how they have work in the past with the change things before they test.(parts changers).thank you for the reply...i really do appreciate it.

 

[Joe Reeves]

Re: 1989 johnson 70hp fires for a second

As Tash states, it sounds like the flywheel key has sheared. The following may also be of some use to you.

The flywheel key is the woodruff key that is inserted into the slot near the top of the crankshaft taper. Its purpose is to keep the flywheel (and its magnets) aligned with the crankshaft so that the ignition functions exactly as it should.

If sheared, clean up the crankshaft and flywheel tapers if needed before installing a new key. Any transfers of metal from one to the other need to be removed/smoothed out to eliminate any chance of shearing another key.

The usual causes of having that key sheared originally is either that the flywheel nut was not torqued properly (105 foot pounds), or the wrong key was used.

The exact key designed for this flywheel to crankshaft alignment must be used. There can be no substitute! The part number of this key is 307480.

The key must be installed in a vertical position with the engine. That is, the outer edge of the key must be straight up and down, NOT aligned with the crankshaft taper!

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

after removing flywheel what is the foot #'s to tight the flywheel not back up to? i wish i had a book.aggghhhh! i think i read it before in all the forums.wantta say 150 foot lbs not sure.

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

you guys are quik. ill try this and repond with the results thank you for answering my questions before i even post them.It's like your readiing my mind lol.

 

[Joe Reeves]

Re: 1989 johnson 70hp fires for a second

See my reply above.

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

1 -more question do you think i will need a puller or will a few taps and little pressure pop the flywheel?

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

Question? anyknow the size of the nut on the flywheel. i have 1 1/16" but cant check do to boat in storage. wanna know to take proper tools there and save on the gas.....

 

[tashasdaddy]

Re: 1989 johnson 70hp fires for a second

I THINK 1 5/16 think. you will need a harmonic balance puller, with i think 2"x5/16 # 8 harden bolts to go into flywheel. standard will strip out.

 

[yamamarinetech40]

Re: 1989 johnson 70hp fires for a second

You can use a RUBBER hammer to TAP around the wheel while the puller is loaded, but don't ever, ever, use a steel hammer...I've seen old vet techs even do this and lose...

 

[Joe Reeves]

Re: 1989 johnson 70hp fires for a second

Never hit the flywheel with a steel hammer BUT when the center spindle of that puller is as tight as you can get it, hit the top of that puller spindle with the biggest hammer you have to pop the flywheel loose.

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

Well, i removed the flywheel nut (omg) was that hard you look down the shaft and see the key looks good, but can't be sure haven't got the harden bolts to remove flywheel yet.I'm wondering how to test the (stator i think it's called) under the flywheel.Is there a visual thing to look for or test if the key is good? I removed the top plug turned motor to "BTDC" noticed the timing mark seem like it was right on,but no measurment tool was used just my very little commonsense lol.I should be get the flywheel off this afternoon all auto stores were closed last nite. (oh i used a 33mm or 34mm to remove nut could not buy a 1 5/16" socket last nite at murrays. Well thanks for the info anymore would be great. Thank you. Jody

 

[tashasdaddy]

Re: 1989 johnson 70hp fires for a second

the slightest deviation in the key will throw it off. here's 6 pages of test find the page for your motor. "http://www.boatpartstore.com/page28.asp"

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

Well,i removed the flywheel found the key was fine not sheared.I checked to see if anything looked frayed or damaged everything looked to be in order reinstalled flywheel and torqed to 105lbs. is it posible that i have a bad power pak that still get's spark at the plugs. still fires and spuders and backfires..help.....

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

Does this engine have S.L.O.W. and would this mess timing up?
I found the beeper warning alarm thing and upon touching it it was giving me signals like beep beep beep.Holding it another way continus beep signal.maybe im shorting it i dunno, my question is there away to unplug something to test,if it's killing the timing. Thank you! everyone who has help me. Jody

 

[HighTrim]

Re: 1989 johnson 70hp fires for a second

Did you try any of the testing posted by Tasha in his previous post? Do you have a DVA meter? Faulty isolation diodes in the power pack could definately cause the rough running engine.

Sorry , typing at same time.....The horn was activated by wiggling it you are saying?

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

no dva meter here. I did read alot just for education purposes but dont have the meter. Yes wiggling the alarm around causes signal.

 

[skeeter69]

Re: 1989 johnson 70hp fires for a second

Sry haven't posted in few days. money is tight so work on recreation is slow(get my drift) haha. Would like to say again motor was running and in gear with ear muffs on when slowly stoped and would not start and run for more than a few seconds and then backfire.Thinking of getting a new power pak.
What do you think?