Johnson 25HP throttle stiff

poundandahalf

New member
Joined
6 May 2011
Messages
7
Visit site
I have a 25Hp johnson 1981 and the throttle is really stiff. I was going to take the pivot point apart there seems to be a grease nipple there as well. Has anyone else had to do this??
 

steve28

Active member
Joined
19 May 2003
Messages
1,480
Location
Cornwall
www.falmouthgypsy.com
your better off getting some spray 3in1 oil or similar, there are various linkages that can get glued up with old oil and grease. spray whilst turning back and forth (in gear not started helps with more movement)

steve
 

VicS

Well-known member
Joined
13 Jul 2002
Messages
48,307
Visit site
Its quite a complex system esp if you have a tiller twist grip.

Try to work out which part is causing the stiffness

If you dismantle any of it very carefully note beforehand how the spring is hooked up!
 

poundandahalf

New member
Joined
6 May 2011
Messages
7
Visit site
Thanks for the replies. This uses a remote control and I have taken that off to ensure it is the throttle which has the stiffness not the cable. It seems to be compounded at the end of travel by the spring. There is also a screw holding a small fixing on the main linkage to the throttle flap inside the housing. This is never touched during the movement which made me think this is not set correctly either it you manually open the flap it will rev astonishingly high but how do you know if you are over reving?
 

VicS

Well-known member
Joined
13 Jul 2002
Messages
48,307
Visit site
I think make sure that the vertical shaft operated by the throttle control rotates freely. A drop of light oil at the top and bottom would be appropriate.

The throttle operates by firstly rotating the magneto baseplate to advance the ignition timing with very little change in the butterfly valve opening in the carburettor. Once the throttle moves beyond a fast idle setting you should see the butterfly open more quickly

Be sure the magneto base plate rotates freely.

The movement of the base plate is transmitted via a cam on it to a lever which pivots on a pin on top of the intake manifold. Make sure that lever pivots freely. ( it will I am sure, it'll stick with the butterfly open if it doesn't) There is a roller on the part that contacts the cam. Make sure the roller is not missing.

There is a link from that lever to the butterfly valve.

At idle the butterfly should be just open a little but at full throttle it should have rotated to the fully open position.

If no help is forth coming on this forum I suggest you go to the Johnson & Evinrude board on the iboats forums. http://forums.iboats.com/forumdisplay.php?f=24
You should get some expert advice there.
Be sure to post the full model details, including the model number if possible, with your question.
 

poundandahalf

New member
Joined
6 May 2011
Messages
7
Visit site
Thanks for the help. The cam located on the magneto baseplate moves the throttle very slightly. The roller appears to be there. I have included a picture it shows the screw holding a brass stop on the linkage. The way it is set it never comes into contact with the lever and therefore never adds to the throttle opening. If I push it manually the throttle would open approx a further 20 degrees. Is this suppossed to come into contact and make the throttle move to the fully open position?
 
Last edited:

VicS

Well-known member
Joined
13 Jul 2002
Messages
48,307
Visit site
The cam located on the magneto baseplate moves the throttle very slightly. The roller appears to be there.
At full throttle that cam should have moved the butterfly in the carb to the fully open position!

On a different engine but similar principle the photo below shows the roller just touching the cam at the mark that corresponds to idling.
( the bit above the roller and cam on this one is a lockout system for the manual starter, so ignore)

 
Top