One for the pros!!! What on earth..........

moevinrude

Cadet
Joined
Mar 23, 2011
Messages
22
I have a 68 Evinrude 9.5, sportwin.

Hasn't run since last year. Cleaned carb, new plugs, checked coils and points. All looks well. Starts fine, but has a miss. Runs better at higher RPM's but still has a miss.

I removed the plug wires to see if it was a particular cylinder and to my surprise.......it doesn't miss!! No matter which plug wire I remove it settles down. You can certainly tell that is running on 1 cylinder but the miss is gone. With both wires on, it goes right back to missing. I have never heard of this. What on earth could this be???????

As always, thanks for any response!!
 

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: One for the pros!!! What on earth..........

Is it a miss or a lean sneeze???
 

moevinrude

Cadet
Joined
Mar 23, 2011
Messages
22
Re: One for the pros!!! What on earth..........

I am surprised that with all the smart techs on here, that no one has any ideas? Usually this place rocks for answers. I still have faith.
 

dew2

Senior Chief Petty Officer
Joined
May 6, 2010
Messages
674
Re: One for the pros!!! What on earth..........

Got the right plugs? have you put a inductive timing light on it both plugs? Ran it in a dark area to see if a spark is jumping? Removed the plugs to see what they look like?
A miss hi and lo speed may be a short the dark area run may show something,Look closly it could be a tiny jump.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: One for the pros!!! What on earth..........

Explain the miss in detail..... normally if a miss exists on a two cylinder engine, the engine is running on one cylinder to begin with.

Plugs should be Champion J4C or J6C plugs, gapped at .030.

Double check point setting as follows:
(Point Setting Of Magneto Models)
(J. Reeves)

Set the points as follows. Have the flywheel key aligned with the fiber rubbing portion of the ignition points. Adjust the gap so that a .020 gauge will pass thru but a .022 will not. Should there be any question of the points being dirty (touching the contact with your finger would cause them to be dirty), clean them with a small brush and acetone or lacquer thinner.

NOTE: Should the operating cam have a small portion on it with the word "SET" imprinted, align this portion with the fiber rubbing portion instead of the flywheel key.

(Magneto Armature Plate)
(J. Reeves)

If the armature plate has a a loose fitting, wobbling motion (the plate that the points, coils etc are attached to), it is usually caused by a slightly worn support ring. This allows the point setting to change erratically as the armature plate turns.

The cure is to remove the armature plate so that the support which is attached to the powerhead with 4 screws is visible. Then, with a screwdriver and hammer, or some tool of your choosing, and looking straight down at the support ring, make an indentation at what would be called the 12, 3, 6, and 9 O'clock positions. Install the armature plate and check for a smooth turning wobble free movement.

You may need to do that procedure a few times to obtain the proper fit (not too tight, not too loose), but it's worth the effort.

Use a small amount of anti corrosive grease between the aluminum ring and the brass support plate and also on the brass bushing of the armature plate when all is well.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: One for the pros!!! What on earth..........

I think your description of a "miss" is mistaken. Pulling a plug wire off creates a "miss" since that cylinder is not firing. You also have a two cylinder engine so pulling the plug wire on one cylinder will not make the engine run any different than pulling the plug wire on the other cylinder if both cylinders are functioning normally. What you should be concentrating on is what happens when the wire goes back on. If one cylinder is missing (not firing) pulling the plug wire on the other cylinder should kill the engine. So lets get your description of what a miss is.
 

moevinrude

Cadet
Joined
Mar 23, 2011
Messages
22
Re: One for the pros!!! What on earth..........

We work on tractors on our farm,,,,,,,,,,most are 30 plus years old. We are used to checking for a dead cylinder, setting points, cleaning carbs and such. usually when you pull the plug wire from a problem cylinder nothing changes.

In this case, the miss that I am talking about causes the motor to die at low RPM, it makes the whole motor shake when it happens. You can feel it in the throttle and see it with the cowling off.

The plugs are correct and look good after I take them out, the points are set at .020. The lean/rich knob is set so the motor does not lean out. Really wierd that when I take a plug wire off while it is running it changes and the motor does not shake every 3 to 4 seconds. Like I said before you can certainly tell it is running on one cylinder but nothing really happens.

Iwill try some of the suggestions, but this is confusing to me.

Thanks for the help.
 

1946Zephyr

Vice Admiral
Joined
Oct 21, 2008
Messages
5,556
Re: One for the pros!!! What on earth..........

Take a compression test. Both cylinders should be close to each other
 

kbait

Commander
Joined
Nov 13, 2007
Messages
2,446
Re: One for the pros!!! What on earth..........

I don't see any reason it'd actually missfire by spark when both are connected, after your drop testing. I'm sure you tried turning the low speed needle out further to be sure it's not a lean condition. You may have to pull the low speed control knob off to actually turn it more.. can't remember for sure on that one. Good luck!
 
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