Throtle 1989 Johnson 8 HP

[johnsonjam]

The above mentioned motor runs slow. Full throttle is half the speed that I remember as a kid. (Dad passed away and the boat was left to me.)
So I took off the cover and quickly discovered how to adjust the idle screw. But when I push on the thing that the idle screw pushes down on it has all the power it should. I am sure that there is a throttle adjustment but I can't figure it out. So I go around the lake with the cover off and my finger on that thing.
How do I adjust the throttle? I have the mechinacial skills of a four year old but I feel like this adjustment should be easy

 

[Whoopbass]

Re: Throtle 1989 Johnson 8 HP

Check the very end of the twist grip throttle on the tiller handle. The plastic deal at the end can be loosened by turning counterclockwise which allows the throttle to be opened up fully (or something like that).

 

[Vic.S]

Re: Throtle 1989 Johnson 8 HP

The knob on the tiller end (around the kill switch) is only an idle speed adjustment It wont have any bearing on the high speed operation!

I am not sure what you men when you say you have found the idle screw.

In THIS DIAGRAM #31 is the idle adjust screw and #15 is the idle mixture adjustment needle.

When you operate the twist grip the whole magneto base plate below the fly wheel should turn and the cam on it should lift the roller #1 in the above diagram which opens the throttle valve in the carb via the cam follower #3 and the link rod #6 (the throttle valve components are not shown as they are not replaceable parts)

You need to check that butterfly valve in the carb is being fully opened when the twist grip is turned fully. It sounds as though it is not.
(You may have to obtain a manual and carry out the "link and sync" procedure.)

As an aid the photo below shows the cam and roller on a similar ('84 6hp) engine. In the picture the throttle is closed to the idle position. At WOT the cam will have moved to the right and end nearest to us will have lifted that roller to its fullest extent and fully opened the throttle butterfly in the carb

 

[johnsonjam]

Re: Throtle 1989 Johnson 8 HP

I press down on the thing that #31 presses down on and it goes fast.

 

[Vic.S]

Re: Throtle 1989 Johnson 8 HP

You are opening the throttle butterfly valve by hand then.

You need to work out why it is not opening when you turn the twist grip.

Is that link rod #6 in position. It links what you are operating to the cam follower #3. You can just see the top of it in my photo.

is the roller #1 in position.

is the magneto base plate and the cam ( see the photo) moving the full length of the cam and lifting the roller fully?

 

[johnsonjam]

Re: Throtle 1989 Johnson 8 HP

Here is my #31. Shown tightened all the way down. The diagram you refer to does not show what 31 presses down on so I attached a picture. This is the thing that I use to make the engine run faster. It goes down way further than the idle adjust screw pushes it down.
I think I have that all figured out. The point of me bringing it up was just to say that it can run faster than it does.
I am headed out now to snap some more pictures.
Oh also see that screw below the starter rope? #18 it was very loose and gas was leaking out of it. Very hard to get to with tools so I finger tightened it as best as I could and no more leak. Don't know if that has to do with anything.
Thanks for your patients

 

[johnsonjam]

Re: Throtle 1989 Johnson 8 HP

Here is a picture of what I think needs to be adjusted. In this picture the throtle is wide open. That rod is in a hard plastic sleeve. The sleeve screws in and out of the thing that shiny bolt holds there but I don't think that would change anything.

 

[Vic.S]

Re: Throtle 1989 Johnson 8 HP

Yes that could well be the trouble. Its a bit different to mine but not much

The sleeve wont turn on mine ... not sure if it should or not ... but I undo the bolt holding the clip and wind the clip along the sleeve until I get it were i want.
The clip on mine is pretty close to the middle of the threaded part of the sleeve but I think if you move it to the middle you may be moving it the wrong way.

take care if you undo the fitting on the end of the rod. Several little bits there that are easy to lose
THIS Diagram shows the lever it fixes to and all the little bits. I nearly lost the sleeve #12 once!
The clip that hols the sleeve is #33



The more I look at it the less certain I am that you will be able to adjust it correctly on that sleeve.
Can you confirm that the Roller #1 in the previous diagram, and shown in my photo, is not missing.

At idle it should be on the marks on the cam that you can see in my first picture at WOT it should be close to the opposite end of the cam.

That plug #18 on the carb you mention needs tightening.

 

[johnsonjam]

Re: Throtle 1989 Johnson 8 HP

Is this the roller you talk about? It just flops around loose it does not come in contact with anything. Mine is black I am touching it with a fork. I am thinking that somehow the roller should hook up to the thing I push to make it go faster. So it looks like #6 is missing.

I think I need to order parts 1-6
Where part #3 goes down and comes back up and #2 screws into looks like it is broke off and missing.

 

[hambonedodge]

Re: Throtle 1989 Johnson 8 HP

It looks to me like there should be a cable or something that pulls
that thing we pushed to make it go faster,I did not look at it when we were on the water, and I was to drunk when we got the boat out of the water.
That screw with the spring only controls the idle a longer screw would only make it run/idle faster, and you would have to unserew the screw when ever you wanted to go slower.

 

[Vic.S]

Re: Throtle 1989 Johnson 8 HP

So it looks like #6 is missing.

Yes I reckon it is. If you can't see it then it definitely is.

It links the part you have been operating by hand with the part that carries the roller so that when the cam lifts the roller #6 operates the throttle valve

From a different source, because the parts list from shop.evinrude.com won't display, you can see that the part is available and is only $3.46.

Whoops nearly forgot the link

http://www.crowleymarine.com/brp_parts/diagrams/19096.cfm