1976 70 HP Johnson won't take throttle!!!

[Bonita Sunshine]

I just bought a 15' boat and it has a 70HP Johnson, and the ONLY way I can get it to take throttle and get it to plain out is to operate it from the throttle linkage at the carbs. I can use the fast idle lever on the controls and it starts and idles fine. I don't won't to put thoughts in any ones head but the only thing I can tell thats different about operating the throttle at the carbs. than at the controls is something to do with advancing the timing. Once I get it plained out and the throttle control operating the carbs. and not me, it runs all over the lake like nothings wrong. If you just try and accelerate it from the controls it just immediately bogs down right off idle.

 

[Joe Reeves]

Re: 1976 70 HP Johnson won't take throttle!!!

Assuming that the compression and spark are as they should be, that problem is caused by either a sticking timer base uinder the flywheel OR fouled carburetors.

 

[mrcj001]

Re: 1976 70 HP Johnson won't take throttle!!!

It sounds like your carb,cables,and spark advance is all out of wack. Probably needs a link & sync.

 

[R.Johnson]

Re: 1976 70 HP Johnson won't take throttle!!!

With the engine shut off, shift it into forward gear, you may have to turn the prop by hand to make it go fully into gear. Push the remote control lever into the full throttle position. At the engine, see if the ignition stator plate is at full advance, and carb throttle plates are fully open.

 

[Bonita Sunshine]

Re: 1976 70 HP Johnson won't take throttle!!!

Mr. Johnson,
When I do what you said the timing advances quite a ways, I'm going to say about a half an inch before that device hits the carb linkage and starts to open them. Needless to say at wide open throttle using the control lever the carb's still lack roughly that same amount being fully open. Obviously this is a problem. So now I ask, my timing getting way ahead of my throttle could cause my problem? If they are adjusted correctly does the timing advance first, or a little throttle before the timing starts to advance?

Mr. Reeves
The timing base moves freely, what would be a good compression reading for a 32 year old 70 HP Johnson? These carb's have no air/fuel mixture screws, they have fixed jets, correct? On the spark, you want me to see if it has a good healthy one correct?

Thanks JRP

 

[R.Johnson]

Re: 1976 70 HP Johnson won't take throttle!!!

The linkage has to be in proper adjustment, that is what the correct service manual is for. I can't explain the whole procedure here.

 

[Bonita Sunshine]

Re: 1976 70 HP Johnson won't take throttle!!!

I have a Clymer manual, I'm possitive it's not as good as an actual Johnson Service Manual like boat mechanic has in his Library. But if you would please tell me a little about how it all works I can figure it out.

Thanks, JRP