Crosbyman and Dave B. – Thanks for all the info! Just what I needed! I’ll be digging into the motor again today or tomorrow.

Dave Stanton (Outbdnut2)

Everything checks out with an Ohmmeter, except the secondary of the coil is an open circuit. It’s a brown coil. I have a one year newer (1971) 7.5 HP parts motor with one good green coil. Can I swap the green coil for the brown one? or is the CD voltage pulse incompatible with the green coil?

Dave

Thanks for the insight. I tested with a screwdriver held into the output tower of the coil and a test lead on the screwdriver – I can see that the screwdriver is touching the internal brass connector I’m holding it against with pressure. I removed the coil and put the other lead right on the now -exposed ground wire. I also checked the spark plug wire and continuity is great. I’m a retired electrical engineer with a lot of TV stereo repair background in a past life, so I understand making good contact and eliminating bad wires, etc. The coil secondary is open no matter how hard I try to insure a good connection, one of the green coils from the parts motor is also open, and physically damaged; and the other green one tests fine with the same test method. Can I use the green one? Otherwise I have a couple more parts motors I can dig out and see what they have for coils, but I have to move several motors to get to them. I also understand that resistance check is not a perfect test for coils because spark could be jumping inside then through bad insulation.
Dave

The part number is close ,but not quite the same on the brown and green coils. Note that in the manual pages you posted, Crosbyman, it gives slightly different resistance readings for “Green” , and “Brown”, while red and brown coils are the same readings. These values are all in the same testing info tables, so there is a difference. The green has slightly higher resistance readings for the primary, and 5 to 6 times the resistance in the secondary. I’m thinking a lot more secondary turns will step the spark voltage up higher, but I don’t want to risk an artifact getting back on the primary and killing the stator. The green one was probably made for a different pulse voltage from the capacitor.

I’ll check my other parts motors for a brown one, and if I can’t find one, I’ll probably try the green coil.. This motor is not worth $180 for a new coil. No aftermarket ones show up.

As long as I’m on here again, I’ll “FYI-mention” that the capacitor must be potted up in the stator, as it’s not there and does not show on the parts list or exploded view.

Some day , maybe I’ll learn to tell people “no” when they have a Mercury to work on – they take way more of my time than OMCs and Champions.
Dave