18hp 25hp Johnson Flyweel

[TM123]

I Have A 68 18hp And A 72 25hp The Guy I Got Them From Said They Were The Same Except The Intake And Carb. He Swaped A Bunch Of Parts And Never Got Them To Run. Now I Have Them But I Dont Know Which Flywheel Gos Where. One Has One Mag Inside And The Other Has 2, 180 Deg Apart. Will They Interchange, And Why 2 Mag.

 

[R.Johnson]

Re: 18hp 25hp Johnson Flyweel

Both these engines' have what is called a high tension magneto, that is, if you have the years correct. The flywheel with two magnets' will work on either engine. The flywheel with one magnet is for a later engine with a low tension magneto. This magneto has the ignition coils mounted on the cylinder head

 

[F_R]

Re: 18hp 25hp Johnson Flyweel

Um, you wouldn't have that mixed up would you? Isn't the two-magnet one for the low tension mag with coils on the head and one driver coil under the flywheel? Takes two magnets to energize that driver coil twice, 180 degrees apart.

 

[R.Johnson]

Re: 18hp 25hp Johnson Flyweel

F R:

Thanks for straightening that out.I hope the owner caught this.

 

[TM123]

Re: 18hp 25hp Johnson Flyweel

I Think I Understand, But I Don,t See Any Evidence Of Any Coils On The Head Of Eigther Motor.

 

[TM123]

Re: 18hp 25hp Johnson Flyweel

There Are 2 Coils Under Both Flywheels, Thats It. the 2 coils under the flywheel have plug wires direcly to the plugs. i just ordered 2 new ones.and in the parts dia. it does'nt show any thing else. it shows the same for the other motor.

 

[F_R]

Re: 18hp 25hp Johnson Flyweel

I guess we got you confused by talking about both systems. You have the high tension magneto. The low tension magneto came out after your motors were built.
High tension: coils under the flyweel, one magnet flywheel
Low tension: spark coils on head, driver coil under flywheel, two magnet flywheel.
Got it?

 

[TM123]

Re: 18hp 25hp Johnson Flyweel

Thanks For All Your Help. Hopefully I Can Get These Motors Running With Your Advice, If NoT I'll Be Back.

 

[samo_ott]

Re: 18hp 25hp Johnson Flyweel

Long live the high tension magneto!

 

[F_R]

Re: 18hp 25hp Johnson Flyweel

Amen!!

 

[gmceieio]

Re: 18hp 25hp Johnson Flyweel

New to the fourm and noticed your thread.
I have a 59 Johnson Sea Horse with no-spark. Is the problem at the coil?
I pulled the plug wires off and there was no spark.
Next thing: Where do I get a coil for this old (sweet) motor?
Thanks, Wishbone

 

[F_R]

Re: 18hp 25hp Johnson Flyweel

Please start a new thread instead of tacking onto an unrelated one. But to answer your question, 1959 OMC motors are notorious for having bad coils. They sell new ones right here at iboats.