crosbyman wrote:

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.

 

Q:  are you saying the capacitor has been taken out ???could you replace it with  one mounted anywhere it can fit. I suspect it would not even have to be under the fw as long as it can be wired to  whatever it is protecting or  unloading into.

 

docs  refer to a . 5uf   800v cap . of phase maker ignition .

What I’m saying is that there is no capacitor, and the parts list does not show one, so I’m assuming it’s potted up with the rest of the ignition stator electronics. The green (+) wire to the coil that would be connected to the capacitor comes out of the underside of the potted electronics portion of the stator. The white wire to the coil (-) comes from the white insulator on the points, so the points ground that wire, completing the circuit when they “make”.
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No capacitor shows on the parts list or exploded view in the link below. (I hope I put the link in right – I haven’t posted a link here for a long time)- am I missing something? Maybe the capacitor was moved out of the potted stator area a year or two later to make it replaceable without replacing the whole stator electronics assembly. There are no signs of any way to mount or wire a capacitor like other old Mercs have.
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I just downloaded the shop manual and for this 1970 motor, it has the Thunderbolt Ignition, not the Phase Maker. It shows the Phase Maker came in 1971. My Thunderbolt is on shown on pages 3D-29 and 3D-30, except one set of points since it’s a one cylinder.
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https://www.marineengine.com/parts/mercury-outboard-parts/40-1-cyl/2498136-thru-3296136-usa/flywheelstator-and-ignition-coil-40

I just found on page 8-25 of the shop manual, it states in the capacitor/stator test table that the capacitor on the 1970-71 4 HP, 7.5 HP, 9.8 HP, and 20 HP motors is part of the stator

. So that verifies what I’m seeing – no external capacitor that can be replaced.
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I also learned the “reddish-rust” colored coils ( I assume this means the brown I have) are for the Thunderbolt ignition and the green coils are for the Phase-maker ignition. Reading the detailed description of how the “First generation Mercury CDI ignition works” that Crosbyman sent me in his first reply, in the system diagram on the 3rd page there is a small note that says: “Works with Orange, Red, or Green ignition coils, but not Black or Blue due to grounding differences”, so based on that, since the existing brown coil (or maybe that is the reddish-rust color mentioned in the shop manual) has the same grounding as the Orange, red, and green coils, I’ll assume I can use the green coil from my 1971 7.5 HP Parts motor. I’m going to try it!
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Sorry to get so wordy in these posts, (thanks for your patience) but I keep finding more tidbits as I dig through the manuals. I’ll let know in a day or two if the brown to green coil swap works!

Thanks again for all the input!
Dave

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crosbyman wrote:

stuff on thunderblot…phae maker

(21) 1971 Mercury 7.5 Phase Maker Learnings | Boating Forum – iboats Boating Forums

– Current condition is No spark.
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Yes – I had previously found that diagram that you sent me showing the capacitor. That appears to be an old-school standard magneto – notice how the spark plug wire comes from a coil under the flywheel, and no charge coils, etc. I think they changed to the Thunderbolt CDI sometime during that range of serial numbers, so put both types of ignition in the documentation for that serial number range because there is nothing like the parts in that diagram in the motor I’m working on, but the diagram at the link below is what I have, and a testing table in the 1966-1974 shop manual verified that the capacitor is potted inside the stator . My 1971 7.5 HP “parts motor” that I pulled a green coil from also has no replaceable capacitor, and the shop manual references show that in 1972, the capacitor was put in as a separate, replaceable part. Maybe they moved the capacitor outside the potted stator circuit because it was failing often?
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I tried the green coil that ohm-tested OK from the 1971 7.5 HP parts motor in the 4 HP yesterday and learned the green coil has the ground wire coming out of the opposite side than the reddish-brown one in the 4 HP. No problem – I sanded some paint off the metal that side mounts to and verified with the ohmmeter from the spark plug wire to ground that the coil ground was in good contact with the engine block. Still no spark. The two resistance checks in the shop manual on the stator wires tests OK, but analyzing the circuit potted inside the stator, that test only verifies that diodes are good, and does nothing to test the capacitor, which could have failed open and that test would still look good. (Note I was an electronic circuit designed for 35 years, so can understand the circuits well).
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I just looked at your link to the iboats forum and found it interesting that a coil can have open resistance in the secondary and still be good, but I’m thinking a small break in a wire in the secondary somewhere inside the coil may create an open that the spark can still jump across; much like you can pull a spark plug wire part way off an engine and the spark will jump the gap you created and the spark plug gap, but I wouldn’t trust a coil like that too far! In that link it gave the method of shorting the points to test the stator, and yes – that makes sense – a meter should read the charge voltage to the capacitor when tested that way, as long as the capacitor hasn’t failed as a short, and I’m thinking turning the flywheel with a drill is a good way to get that meter reading – Thank you! I will try that, and if that looks OK, in the next couple days, I’m going to haul my oscilloscope to the garage and look at the signal to the coil primary, as that will verify the stator’s condition, and compare it to the scope diagram shown in the CDI Maker-point ignition writeup you sent me in your first post.
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This motor has taken way too much of my time, but I’ve learned a lot, and now it’s turned into a personal challenge to either get it running, or verify beyond a doubt what is wrong. If the stator is bad, it’s not worth fixing and I don’t have a one cylinder stator in a parts motor. I hesitate to search for a used stator, as it’s difficult to know I’m buying a good one. New ones cost more than the motor is worth.
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Here is a diagram of what I have: https://www.marineengine.com/parts/mercury-outboard-parts/40-1-cyl/2498136-thru-3296136-usa/flywheelstator-and-ignition-coil-40
Thank you!
Dave

crosbyman wrote:

I agree that some expensive parts may exceed the value of the motor but when one looks at the purchase price of a new engine plus taxes the investment  in a staro take a different perspective.

Most of these old motors have lots of life in them  if mecanically sound.  and reviving one  is a lot cheaper than buyng new.

Patience brings joy 🙂

 

btw  did you check Dave Bernard’s suggestion on the insulator blocks ….Dave is an expect on Mercs …looks for  small cracks !

 

Yes – I checked the insulator block and it is fine and electrically is Ok too.
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I appreciate your comment, and I get the value compared to price on new motors, and I like the old ones better (hey – it’s one of my hobbies!), but the owner of this one got it from a relative, doesn’t have extra money to put $300 + into it for a stator, and doesn’t really need the motor because a couple years ago I restored a 1956 3HP Evinrude for him that he uses. He may give or sell it to me, but I don’t have much interest in putting much money into it because I have over 90 motors from 2 to 40 HP (I live on a lake), and a lot of them are waiting for resto, and there are several of my motors (mainly OMCs and Champions) I’d rather be fixing up. My next project will be to try to make two good running 1955-56 15 HP Evinrude Fastwins out of three that I have, and set them up on a 1957 Crestliner Viking14 as a dual setup. I have a dual remote control box.

I’m 95% sure the stator is bad, but I’ll see what the oscilloscope tells me before I totally give up.
Dave