1971 400 merc. coil problem

[froghill]

I've got a 40 hp merc, ser. # 3,305,415, And have come to the conclusion that I have a bad coil. This is the large coil on the frame that has the spark plug lead to the distributer. Ther is no continuity thru the tower to the frame. I have a weak spark , but on correct time . I have tested the trigger, and the stator coils and all have correct ohms . I don't seem to be able to locate this particular coil . Can I use another and not blow the switch box or do I have a black boat anchor? Any help will be great!

 

[usskydvr]

Re: 1971 400 merc. coil problem

What is the part# on the ignition coil?

 

[froghill]

Re: 1971 400 merc. coil problem

master tech gave me a # I believe its mercs. 332-475A1 Is there a definite check for bad coil. No continuity thru tower should clench it ?

 

[usskydvr]

Re: 1971 400 merc. coil problem

I think there is a digit missing. Normally the form is a-###-####A1 or A#
Either way I need to know what you currently have, not what a relacement # is. I would expect something like A-397-361 or A-398-2245
.or A-394-1128A1. Generally primary resistance is less than 1 ohm. Secondary is about 50 ohms. But each coil model is slightly different.
You may also be abor to fine the Mfg name and Mfg #. Scintilla, Phelon, Fair-Morse, Kiskhafer, etc..

 

[usskydvr]

Re: 1971 400 merc. coil problem

For A-332-4075A1
Primary Pos (green wire) and Gnd = 0 ohms
Secondary Coil tower and Gnd = 24K-30K ohms

 

[froghill]

Re: 1971 400 merc. coil problem

I can find no #'s on the coil itself . I guess I need to get ahold a parts catalog for this engine to give that info. The unit is shiny black with a very heavy primary lead(green) I believe it must be original , its pretty old looking . I look around on the web more to see if I can get that correct #. Thanks for reply

 

[froghill]

Re: 1971 400 merc. coil problem

Boats.com has a diagram at model # 1400101 under 1971 mercury outboards showing part # 4075A1 must be there nomenclature, so no help there , but at least it shows the actual pic of part. Still looking for merc original part #.

 

[usskydvr]

Re: 1971 400 merc. coil problem

The web and Merc parts diagrams and Service manuals won't give you the actual Mfg part #. That can only be found on the coil itself. You may have to remove it to look on the underside. At any rate, you should have some continuity from the Coil Tower to the frame of the coil itself. Otherwise the coil is bad.