Topic: td20 crankshaft question – Antique Outboard Motor Club,Inc

This topic has 5 replies, 4 voices, and was last updated 7 years, 10 months ago by Buccaneer.

Viewing 6 posts - 1 through 6 (of 6 total)

Author

Posts
March 17, 2017 at 12:43 am #6552
20mercman
Participant
US Member
I have a bunch of td20, and tn26 and 27 parts and i’m trying to turn it all into at least one running motor, I came across a crankshaft in my parts stash that has the correct part number for a td20 crank (301670). however, it has an unusual cam design and the flywheel key way is clearly different than any other td20 or tn that I have ever seen. a rotor type ignition will definitely not fit and the modern omc ignition uses a cam that slips over the shaft, not ground into it. can someone tell me what I have or what kind of ignition system is needed?
thank you.

Attachments:
March 17, 2017 at 4:32 am #54442
hotrod
Participant
That crank is probably for a TD-15. To use it, you must also use a maverick spark suppressor for each coil. The TD-15 crank cam flat spot is nearly 1/2 inch wide from its leading edge to its trailing edge. The TD-20 crank has a cam flat spot which is 3/4 inch wide. The magnet rotor for the TD-20 crank is stronger and it is marked by a ‘V’ cast on top. This TD-20 rotor may be used with the TD-15 crank only if suppressors are used and only if they are in good condition. The older magnet rotor without the ‘V’ cannot be used in the TD-20 under any conditions. TD-20 models do not use maverick spark suppressors due to the wider cam flat which prevents erroneous sparks. There were 2 styles of suppressors in the TD-15. The first style suppressor on the TD-15 model had an exposed spark on the mag plate where the coil ground wire went towards ground. The second style had a suppressor that enclosed the grounding spark inside of it.
March 17, 2017 at 12:00 pm #54444
Buccaneer
Participant
US Member
Interesting about the Maverick Spark Suppressors. As I was
working on the HD-25, I just read about them in the service
manual, but the photo wasn’t good enough to see what they looked like.

Prepare to be boarded!
March 17, 2017 at 7:13 pm #54472
garry-in-michigan
Participant
Lifetime Member
I believe Mumbles put this up a few years back. . . 😀
March 17, 2017 at 8:14 pm #54475
20mercman
Participant
US Member
Alright thank you for the input. I might just end up looking for a good td20 crank then, if anybody has one they want to get rid of or want to trade for this one just pm me. its really in great shape just doesn’t match the junk that I have. 😆
March 17, 2017 at 10:23 pm #54484
Buccaneer
Participant
US Member
Garry, thanks for the photo. Is the "tab" that the spark is arcing to,
and the capacitor, both part of the suppressor?

Prepare to be boarded!
Author

Posts