1978 70 hp Johnson throttle problem

[Tassie 1]

I have a 1978 70 hp johno project motor on a boat.
It starts and runs but at or near WOT.
l know that is not good.
Lol
Choke works as it should
No matter what l do l cannot get the throttle valves to stay closed using the controls or even move the valves using the throttles levers.
Using the throttle itself does not move the valves

Is a later model control box and cables.

I feel there is a linkage missing but cannot see it on that years schematics,
Anyone have a working crystal ball ?

 

[racerone]

Disconnect throttle cable at the motor.-----Will it idle now ?-----How did this motor run for you last season ?----Any pictures of linkages ?

 

[Tassie 1]

Sorry, had grandpa duties,
I 've only had it going on a stand, not in the water
No pics as yet.
When carbs are disconnected at motor moving the carb linkage does nothing...shutters do not move.
They move when choke is activated though.

Thanks for the quick reply.

 

[racerone]

Really.------The choke flappers are at the front.------Throttle plates are way in the back of the carburetor throat.----Are you saying those do not move ?

 

[Faztbullet]

First thing get yourself a OEM manual

 

[Tassie 1]

4.00 am here.
Couldn't sleep...had a cuppa.
Yep, it is the flappers at the front of the carbs.
Moving the linkages does nothing to those.
Roll pins on the otherside move as they should.
Flaps only move if you push them with fingers etc
Choke ( electric and manual ) works.

Weird.
I've found a set of '81 carbs in the shed and when this weekend's shenanigans ( sons wedding ) are over l will put those on as they seem to be working properly.
This boat has been relegated down to tender duties to get out to a moored flybridge cruiser, hence the $100 project motor but has been on the backburner for awhile due to other stuff happening.
We have other boats as well so have been using those up to now.
Will get a proper manual asap.
I prefer hardcopies.

Thanks again

 

[racerone]

From where I sit it sounds like everything is working as designed.-----Get the manual.----Read it before opening your tool box to work on these simple carburetors !