1966 Johnson 60hp Magneto Ignition question

Actually two questions, I am trying to troubleshoot a tachometer problem. First let me say the engine is running perfectly. The Tach Airguide (with sending unit) is pegging out at anything after about 800 rpm. I am trying to narrow my issue down to the tach or ignition. Now for the 2 questions: Does anyone have the parts diagram (exploded view) for a magneto ignition? My 1966 parts diagram only includes the "Distributor group" or automotive type ignition. The 2nd question is more of theory verification. If I understand how the tach works correctly it basically is reading the number of pulses coming from the ignition (how fast the points are opening the closing). Is it possible for the engine to run correctly but for the engine to not pulse or for the signal to be "grounded out" by something? I'm thinking the signal is being interrupted somehow. Thus the reason for the Magneto diagram. I sent the tach out for a function check and it came back working/operational. Really at a loss, any help would be fantastic.

Re: 1966 Johnson 60hp Magneto Ignition question

There is a diagram here:
http://www.marineengine.com/parts/v...ntage-evinrude-johnson/278784/27878400001.htm

Re: 1966 Johnson 60hp Magneto Ignition question

Thanks tx1961shaler! That's exactly what I was looking for. I'm guessing that coil is "grounding out" against the housing and causing the interference with the Tach. Thanks again!

Re: 1966 Johnson 60hp Magneto Ignition question

I reckon your guess is as good as mine, but I really don't think it is a coil problem. Shouldn't run well if anything wrong there. I suppose you have verified that you have the correct transmitter (?). Perhaps you should read this:
http://www.classicboatwork.com/clas...e/airguideinstructions/Airguide_Instruct.html

Re: 1966 Johnson 60hp Magneto Ignition question

Thanks for the suggestion F_R. I should have mentioned the tach was working correctly prior to me doing a tune-up (Points, condenser & Rotor). I have verified I do have a matched set (transmitter & tach). I think I'm going to take the magneto apart and inspect everything.

Re: 1966 Johnson 60hp Magneto Ignition question

Possible points set slightly off, reset as follows unless you have set via ohm meter and point set marks.

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

Set the points as follows. Have the high lobe of the cam aligned with the fiber rubbing portion of the ignition points, with the points opened maximum. 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.

If you changed the rotor..... note that the V4 magneto rotor differs greatly from the automotive type V4 rotor but is still overlooked from time to time. The magneto rotor has a larger "hook" type business end to it whereas the automotive rotor has a straight screwdriver type business end to it. The two are absolutely NOT interchanable.

Automotive rotor = 580338

Magneto rotor = 580260

Re: 1966 Johnson 60hp Magneto Ignition question

So just to follow up with everyone, it was infact the tach itself. I got a replacement sending unit and it corrected my issue. Thank you to everyone for all of your help.