64' evirude lark 40hp- not accelerating well

[johnm5858]

I have been trying to get this 40 hp lark going better, it has been worked on by several mechanics the latest discovered some broken link pins and repaired. I just had it out on my 14 runabout and it does't seem to get up to full acceleration. The high speed carb jet is all the way over to rich. When I brought it back in today I found this little lever with a near the accerater, it has a cylinder that spins on the top of it, when the throttle shifter is in med. or low this spinning cylinder is pushed against another moving wheel but when I moved the throttle to high this level with the wheel was lose, as if it is missing a spring? Is this the cause of the poor acceleration?

 

[itstippy]

Re: 64' evirude lark 40hp- not accelerating well

That little lever with the rubber wheel on it that rubs against the big cam is the main throttle control for the carburator. It is (or should be) spring loaded so it's always rubbing tight against the big cam. If it's loose and not held tight against the big cam at all times then either: 1) someone's left a spring off, or 2) the carb's linkage is hooked up wrong, or 3) the carb linkage is so gummy that it's sticking. There is no way to fine tune a carb in such a condition. It's been worked on by "several mechanics"? Yikes. You should go to the local library and see what they have for maintenance manuals on older Johnson/Evinrude motors. Most have a Seloc or Clymer or Glenn's you can borrow. They all have exploded diagrams of the carburater's parts, and pictures of what it should look like put together. They also have step-by-step procedures for disassembling the carburator, cleaning it, and putting it back together. You should read and understand that chapter, whether or not you do the work yourself. It's really pretty simple. You have carburator issues and you can't tune a carb unless all the necessary pieces are in their proper places and moving freely.

 

[jimmbo]

Re: 64' evirude lark 40hp- not accelerating well

On the old 40hp, the cam follower(rubber wheel) only touched the cam up to the point of max timing advance. Once that was reached and the throttle lever was pushed further, a spring loaded link pushed the carb butterfly open and in doing so the cam roller no longer was in contact with the cam

 

[johnm5858]

Re: 64' evirude lark 40hp- not accelerating well

On the old 40hp, the cam follower(rubber wheel) only touched the cam up to the point of max timing advance. Once that was reached and the throttle lever was pushed further, a spring loaded link pushed the carb butterfly open and in doing so the cam roller no longer was in contact with the cam

 

[johnm5858]

Re: 64' evirude lark 40hp- not accelerating well

so as the throttle is advanced in high the cam no longer touches the big wheel? One other reply said it should always be touching the big cam. It does seem to be missing a spring which would seem to keep the small wheel in touch with the cam at all times.

 

[Paul Moir]

Re: 64' evirude lark 40hp- not accelerating well

Jimmbo is correct, the roller is supposed to be pushed off the cam by the auxiliary linkage when the armature plate (the thing the cam is mounted to) hits the timing stop and stops moving. That occurs about 2/3 or 3/4 full throttle.
What work has been done on your outboard? Why do you say the main jet is very rich? Do the spark plugs indicate it?
I can take a couple pics of the linkage if you think it would help.

 

[jimmbo]

Re: 64' evirude lark 40hp- not accelerating well

so as the throttle is advanced in high the cam no longer touches the big wheel? .

There is a link(1/8 " rod), on the port side of the engine. One end is connected to the throttle valve assembly on the carb, the other end slips into a guide on the throttle linkage on the port side of the engine. On this link should be a adjustable stop. Once the ignition is fully advanced, the guide contacts the stop and pushes the link further opening the the carb. This was called the fuel saver linkage. The cam follower is connected to the linkage and lifts away from the cam. There probably is a spring to pull the rollor against the cam. I remember adjusting this linkage on my dad's 1963 40hp but it was 30 yrs ago