1968 18 HP Evinrude ignition timing

[mobydick]

Is it possible for the ignition timing to be off and if so, how is it adjusted.

I have replaced every component of the ignition, removed wobble from the armature plate, rebuilt the carb, checked the compression and still am having low power output.

Any other suggestions are appreciated. I am at a loss at this point.

 

[F_R]

Re: 1968 18 HP Evinrude ignition timing

Is it possible for the ignition timing to be off and if so, how is it adjusted.

I have replaced every component of the ignition, removed wobble from the armature plate, rebuilt the carb, checked the compression and still am having low power output.

Any other suggestions are appreciated. I am at a loss at this point.

It is more or less impossible for the timing to be off, as long as it has spark. The throttle control rotates the armature plate up against the stop for full advance. Is that happening? Let's see, as I remember, the stop is the notched plate on the armature plate that goes up aginst the shifter interlock.

 

[mobydick]

Re: 1968 18 HP Evinrude ignition timing

yes, I have already checked all the linkage and throttle cam. The throttle cam and linkage connecting the armature plate to the throttle are have slots rather than holes where they connect to the armature plate. I thought perhaps this was an adjustment for timing since moving the linkage mount on the slots could affect timing a couple of degrees.

 

[Daviet]

Re: 1968 18 HP Evinrude ignition timing

what exactly do you mean by "low power putput". Does the engine not rev up to proper RPM?

 

[mobydick]

Re: 1968 18 HP Evinrude ignition timing

correct, it does not get up to full rpm. I know the prop is not spun, it is a new prop that I tested on another engine.

It is as if the throttle is only half way open even though it is all the way open. I have run with the cover off to observe the linkage moving properly

 

[Daviet]

Re: 1968 18 HP Evinrude ignition timing

When you rebuilt the carb did you remove the high speed, clean and blow out with compressed air? You might try squirting some fuel mixture into carb and see if it picks up. Has this motor always been on the boat you are running it on? Have you changed the prop size for some reason?

 

[jbjennings]

Re: 1968 18 HP Evinrude ignition timing

My guess is that you have weak spark on one plug. If you've not checked it with a spark tester and actually saw it give at least a 1/4" blue hot pop, then it's not good enough. I've had this problem quite a bit and until you get the spark right on both cylinders, it won't run WOT.
Good luck,
JBJ

 

[sbump52]

Re: 1968 18 HP Evinrude ignition timing

Guys does this one have the plate under the flywheel that a cam rides on to open up the throttle butterfly like my 55 10hp? Mine was way off and it wouldn't get past half speed. Someone had moved it way out of place.

 

[lindy46]

Re: 1968 18 HP Evinrude ignition timing

Yup, could be that cam is not adjusted properly. There is a mark on the cam and the follower (rubber wheel) should just start to open the butterfly when the wheel hits the mark. When throttle is fully advanced, butterfly should be fully open (horizontal). If not set properly, loosen the bolts which hold the cam to the armature plate, and adjust.

 

[kbait]

Re: 1968 18 HP Evinrude ignition timing

Get or make a spark tester (search this forum..) Confirm 1/4" lightning bolt for each cylinder, and continue. Spark is weird, and assuming it's good can waste time.. and always use check continuity of closed points by using a multimeter before hooking coil/condenser wires to the points. Snap it and try a few times to be sure. A fingerprint can gum it.

 

[outlaw241]

Re: 1968 18 HP Evinrude ignition timing

i had same problem an it was the control lever,the vertical linkage that slips in a the back of tiller handle it has two flat blades on it that drives the control lever,one of the blades was broke. you should be able to tell with the engine not running put it in gear an turn to wot an the roller should start up the cam almost to the highest point. i hope this helps the part that was broke on mine is called a control lever pin.

 

[mobydick]

Re: 1968 18 HP Evinrude ignition timing

on both cylinders the spark is vibrant blue and jumps a 3/8" gap with no problem. The issue is not spark related as far as I can tell.

Daviet, this is the same size/ pitch prop and same boat the motor has always been on. I did blow out the mainjet when I rebuilt the carb but I'm going to try your idea of squirting fuel mixture into the carb at full speed. At least this could help determine if this is fuel or ignition related problem.

sbump, lindy, and outlaw these are suggestions worth looking at. I will check them out

Thanks everyone for the input. I like a challenge but this is getting frustrating.

 

[mikesea]

Re: 1968 18 HP Evinrude ignition timing

are you sure the timing plate is advancing fully,if i recall there is a sliding barrell lock on a rod that can come loose,and,sometimes the roller will break off,are you certain it still has the correct rubber roller,and not just riding on the shaft the roller goes on

 

[mobydick]

Re: 1968 18 HP Evinrude ignition timing

Here is a summary that will hopefully fill you in on everything I have done so far.

I have replaced the plugs, wires, points, condenser, and coil.
The champion plugs are gaped to .030
The points are gaped to .020.
The carb has been rebuilt. I disassembled it completely including jets, tubes, seats, needles etc and soaked in carb cleaner. After removing from the carb cleaner, I rinsed with gasoline. Then I blew out every orifice with compressed air.
I checked the compression and get about 95 psi in one cylinder and 98 psi in the other.
I checked the spark and it is hot blue and jumps a 3/8" gap no problem.

I worked on the motor this afternoon to double check everything and made an interesting discovery. When the throttle is turned to full so that the stop on the armature plate hits the stop on the shift inter lock and the throttle cam is at the max, the throttle valve goes beyond horizontal in the carb throat and continues until it is about 1/3 closed.

Is this normal or should the the throttle valve be stopping in a horizontal position? It seems to me that this could certainly decrease performance but I can not see how it could be adjusted.

Thanks for all your suggestions so far.

 

[asdasc]

Re: 1968 18 HP Evinrude ignition timing

That seems odd, for sure. I think you may be onto something.

 

[lindy46]

Re: 1968 18 HP Evinrude ignition timing

I worked on the motor this afternoon to double check everything and made an interesting discovery. When the throttle is turned to full so that the stop on the armature plate hits the stop on the shift inter lock and the throttle cam is at the max, the throttle valve goes beyond horizontal in the carb throat and continues until it is about 1/3 closed.

Is this normal or should the the throttle valve be stopping in a horizontal position? It seems to me that this could certainly decrease performance but I can not see how it could be adjusted.

Thanks for all your suggestions so far.

Loosen cam and adjust so throttle opens fully and no more.

 

[mobydick]

Re: 1968 18 HP Evinrude ignition timing

I loosened the cam, actually took it off so that I could look at it and understand how the adjustment worked. The bolt at the high speed end goes though a hole so that end cannot really be adjusted. The bolt at the low speed end goes through a slot so there is about 1/4" of adjustment on that end. If I slide the low speed end of the cam out all the way it obviously increased the low speed throttle actuation. It also caused the high speed end to pivot in some so it slightly decreases the high speed actuation but not enough to keep the throttle valve from over rotating.

It does not seem right that I would have to create a slot at the high speed bolt hole on the cam but any suggestions would be great.

 

[Joe Reeves]

Re: 1968 18 HP Evinrude ignition timing

The cam has a scribe mark on it. The roller should make contact with the cam when that scribe mark is dead center of the roller. However, whether this alignment is correct or not, this would not cause the throttle butterfly to pass the wide open throttle (horizontal) position at the full throttle setting.

The 1968 18hp carburetor throttle shaft is equipped with a permanent link on the end of the butterfly shaft that the linkage rod connects to, there is no adjustment. That linkage rod connects directly to the throttle roller arm shaft. For the throttle butterfly to exceed the horizontal position with this setup, either the linkage rod is wrong (too long) or the throttle roller shaft assembly has been bent, something of that nature.

Is it possible that another carburetor has been installed, one that has a separate linkage arm that attached to the end of the throttle butterfly shaft with a set screw? If so, make a proper adjustment at that position.

You state that the engine is a 1968 18hp Evinrude. What is the model number of that engine?

 

[outlaw241]

Re: 1968 18 HP Evinrude ignition timing

on my cam plate is two scribe marks,the roller makes contact with the cam plate but it doesn't start to move the throttle plate until it is centered between the two scribe marks. my model # 18802m

 

[Joe Reeves]

Re: 1968 18 HP Evinrude ignition timing

If two scribe marks, you are correct, and that model number does indicate the engine as a 1968 model.