Surging FD-10

[Basher]

Hi again everyone.

I got a new one for all of you.

My '56 Johnson FD-10 runs great but once in a while it will get a case of the surges. I will be running along, either trolling or wot everything running fine, lots of gas not making any changes to idle adjustments when all of the sudden the motor surges. The surging will last for a short period then seems to resolve itself and off I go again. Is there something I can do to correct this or do I have to live with it.

Any help greatly appreciated.

By the way always carry a spare shear pin for your prop along with two spark plugs with a couple of tools. Wouldn't you know that I had my tools, my spark plugs, my emergency kit and fire extinguisher and two km out in the lake I break a shear pin. Not a good day!!!

Basher

 

[Joe Reeves]

Re: Surging FD-10

Slow surge up and down? Like slowly running out of fuel, then being corrcted?

Fast surge? Like pulling a spark plug lead off, then replacing?

 

[Basher]

Re: Surging FD-10

I am not sure if this will help but it feels jerky, especially at higher speed. There is a noticeable decrease in engine performance, speed and rpms. Each "jerk" last only for a second, runs normal for five to ten seconds "jerks" and then runs normal again. This lasts for two to five minutes and then goes back to normal. It only occurs when the engine has been running for a good period of time ie. 30 mins or more.

I did have a bad spark plug wire that has been replaced, it was rubbing the flywheel, I rewired and replaced with new wire and the entire ignition system is brand new this season (coils, points, condensors, wires, and plugs.) Also the carb has been totally removed, cleaned and rebuilt. As well the engine is running on the old two line pressure tank but that too has been totally restored ground up (sanded to bare metal, repainted, new diaphragm and gasket and new fuel line and o-rings in female connection and new fuel line from male fuel connection to carb and manifold.)

Basher

 

[jbjennings]

Re: Surging FD-10

I guess you feel confident it's not a slipping clutch dog, right?
If not, I'd think a wire was nicked or possibly a crack in a coil where you can't see it that's allowing it to arc every once in a while.
Just some ideas.
JBJ​

 

[DJ]

Re: Surging FD-10

A "surge" is not a prop, or drive issue. It's a lean mixture, or spark issue.

You're losing one, or both. Spark is easy to check, with a timing light.

 

[Basher]

Re: Surging FD-10

I guess you feel confident it's not a slipping clutch dog, right?
If not, I'd think a wire was nicked or possibly a crack in a coil where you can't see it that's allowing it to arc every once in a while.
Just some ideas.
JBJ​

No, it is for sure not a slipping clutch. Definitely a surge or jerk in the power. Could possibly be a intermittent short.

I will open up the flywheel again and check all connections and coils as per your post on the cracked coil. Would it be normal for a coil to crack after only maybe 20 hours of use?


Basher

 

[Joe Reeves]

Re: Surging FD-10

Model FD-10 is a 1956 15hp Johnson. It's possible that the points aren't set exactly right, worth double checking.

Also, you should be using Champion J6C spark plugs, gapped at .030.


(Point Setting Of Magneto Models)
(J. Reeves)

Set the points as follows. Have the flywheel key aligned with the fiber rubber 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.

 

[freddyray21]

Re: Surging FD-10

Joe on that one does the cam say 'set' or "top" I've got one at home and can't remember.

 

[wbeaton]

Re: Surging FD-10

Joe on that one does the cam say 'set' or "top" I've got one at home and can't remember.

Probably "top", but it doesn't matter. Set it just the same.

 

[Joe Reeves]

Re: Surging FD-10

It will no doubt say "top" so that one doesn't install it upside down. The "set" mark came into play quite a few years later on.

 

[freddyray21]

Re: Surging FD-10

just wondered. After all these years most of the motors I have seem to be hybrids anyway.

 

[Basher]

Re: Surging FD-10

Hey all,

I just came in from outside and have pulled the flywheel to inspect everything again. The coil which powers the bottom cylinder looks suspicious to me. The wing on the one side of the coil appears to be expanding between the layers. Not sure if this could cause problems or not. As I mentioned early this coil is brand new. Is this a possible cause of the problem? If so should it be replaced with another new one or let it slide.


Basher

 

[cc67]

Re: Surging FD-10

Model FD-10 is a 1956 15hp Evinrude.

FD-10 would be a 56 15hp Johnson I believe. Basically the same motor.

 

[Basher]

Re: Surging FD-10

Model FD-10 is a 1956 15hp Evinrude.

FD-10 would be a 56 15hp Johnson I believe. Basically the same motor.

it is a 1956 Johnson FD-10 15 HP I am quite sure of this as i have done a complete restoration to the motor in the past year.

Basher

 

[Joe Reeves]

Re: Surging FD-10

Of course the engine is a Johnson, hence the FD designation. Sorry about that....... looking at two pages at the same time in the OMC guide. I changed/edited my original reply to reflect your correction. Figured that would be easier than having you change the paint job and decals (grin).

 

[freddyray21]

Re: Surging FD-10

replace the one coil if you think it might be an issue at least it will tell you something. Also make sure the connection from the wire to the coil is good and you are using the boots that came with the new coils. Are the wires new? check them for fray at rub spots.

 

[Basher]

Re: Surging FD-10

As I mentioned in my earlier posts everything was replaced in the electrical system earlier this spring from coils to plugs and everything in between. I am going to try testing the coil on the bench with my voltmeter.

Basher

 

[Joe Reeves]

Re: Surging FD-10

Having the coil layers expand usually indicates that the outer surface of the coil yoke (metal portion) is hitting the flywheel magnets. Correct as follows.

(Magneto Coil Alignment)
(J. Reeves)

To align the coils properly, have the metal vertical portion of the coil yokes aligned with the inside edge of the bevel that exists on the top portion of the aluminum seat upon which the coils sit. This creates the proper distance between the coils and the flywheel magnets. Faulty alignment creats friction and the yokes of the coils heat up, turn blue and expand.

(Regular Magneto Coils - Continuity Test)
(J. Reeves)

Checking the continuity of the ignition coils....... Have the ohm meter set to High Ohms.

Remove the primary wire from points. Remove the coil ground wire. You do not want either of these wires touching anything.
Connect the black lead of a ohm meter to the spark plug boot terminal, then with the red ohm meter lead, touch the ground wire of the coil.

Then touch (still with the red lead) the primary wire. You should get a reading on both touches (contacts). If not, check the spring terminal inside the rubber boots of the spark plug wire.

If there is no continuity between the secondary circuit (spark plug) wire and the primary or ground, remove the coil from the armature plate, then check the continuity directly between the prong within the coil (prong that the plug wire connects to) and the primary and ground. Poor or no continuity of a coil (or plug wire) is one reason for weak spark, s/plug fouling, or no spark.