1973 Johnson 25HP Timing help

[JGeiman2]

PICS ADDED!!!!
Can anyone help me set my timing. The motor is pretty hard to keep idling and I have had to adjust linkage and screw my tiller screw in all the way to keep it going. Can someone help me with the proper procedure for setting the timing.

Thank you!

I'll try to post pics of the throttle cam and linkage later.

 

[JGeiman2]

Re: 1973 Johnson 25HP Timing help

I've tried looking in the archives for this but i can't find anything...

 

[F_R]

Re: 1973 Johnson 25HP Timing help

There is nothing to set, other than the breaker points gap, which is .020". The timing advances and retards every time you turn the throttle twist grip.

Related to that is the carburetor throttle plate. It must be synchronized with the spark advance. At idle speed it should be completely closed and RPM is controlled only by spark advance/retard.

Have you tried adjusting the carburetor slow speed needle? Sounds like it may be set too rich.

 

[JGeiman2]

Re: 1973 Johnson 25HP Timing help

FR, I've adjusted the slow speed per the carb settings on here. I adjust the needle out until the engine stops coughing and then I fine tune from there. I know not every engine is the same, so there is some fine tuning involved.

When I let the engine idle, the throttle cam keeps spinning (clockwise) and the cam follower goes past the little hash mark on the throttle cam. Does that have to be stopped at the line while the tiller handle is in the SHIFT position? My cam follower stops on the bolt that holds the throttle cam on.

When I hit WOT the cam follower almost crests the throttle cam.

 

[JGeiman2]

Re: 1973 Johnson 25HP Timing help

Pics

 

[JGeiman2]

Re: 1973 Johnson 25HP Timing help

Second pic, the arrow is pointing at the position the cam follower is located when the tiller handle is in the "Shift" position...it's right at the cam bracket bolt head.

 

[JGeiman2]

Re: 1973 Johnson 25HP Timing help

Two more pics...

 

[lindy46]

Re: 1973 Johnson 25HP Timing help

Don't worry about the settings on the twist grip. They are not very accurate and more for reference. You need to look inside the carb throat at the throttle butterfly. When the roller hits the mark on the cam the butterfly should just start opening. When the throttle is fully advanced, the butterfly should be fully open. Have you cleaned/rebuilt the carb?

 

[JGeiman2]

Re: 1973 Johnson 25HP Timing help

Cleaned the carb. Checked to see if the needle valve sealed by blowing into it. It does seal.

So the mark on the cam is where the butterfly should just start to open. I'll check that out this afternoon.

The outboard runs okay but when it comes off WOT it almost always dies.