1971 4hp Merc no spark need help with testing results

[Outboard Mike]

No spark condition. I have done the stator and coil test specified in the Merc 40-75-110 thunderbolt ignition diagram for my 1971 4hp mercury serial # 3030486. I only have a radio shack tester and these are my findings.I disconnected the green stator lead and connected the plus tester to it and the negative tester side to ground. The results were a 58 to 60 on the 1 K ohm scale. I then connected the negative tester to to the green wire and plus to ground. Results were no reading at all.
I then did the coil check with leads disconnected from the ignition coil and HT lead from spark plug. I tested between positive and negative of coil and it buried the needle at 0 ohms. I then connected the tester between the HT lead and gound. Results were a 1.1 reading on the ohms scale. Can anyone tell me why I have no spark?? Is there a problem with the coil or magneto??

 

[Laddies]

Re: 1971 4hp Merc no spark need help with testing results

Could be the points or the insulator block on the point stud is cracked a common problem here's the test for the system this is listed hor a twin but you single is the same. Note the grd note at the bottom of the page.

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

This is the model without points. The thunderbolt III I think.

 

[Laddies]

Re: 1971 4hp Merc no spark need help with testing results

By your serial number the engine is a 1971 and has conventional ign. on it, the single cyl. Mercury's all had points till 1974 both standard and CD ign. There is anouther style CD that uses 2 stator coils, a rectifier bridge and separate capacitor but it still used points. To help we need better info as the serial and ign. you describe don't match try to find a part number off a ign part.

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

The stator plate number is 3383982. The support tower for Magneto is L1411202. The coil bracket is 56188. I had the flywheel off before and there is no points.

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

The stator plate number is 3383982. The support tower for Magneto is L1411202. The coil bracket is 56188. I had the flywheel off before and there is no points.

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

Correction to my last post. There was no condenser when I had the flywheel off. (been working on different motors) I can pull the flywheel and check the points if you think that might be the problem.

 

[Laddies]

Re: 1971 4hp Merc no spark need help with testing results

Sorry but I can seem to identify you system if you will use this link to 4 HP parts book you can and then give me the serial number the book uses to identify the engine. http://www.ishopmarine.com/ishop/js...cCatFilter=MM&eCatSupFldr=supplier-050-025-MM

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

Found the right part number. I went out and looked in brighter light and found the stator is 3363962. The 6 looked like an eight at the angle I was looking.

 

[Laddies]

Re: 1971 4hp Merc no spark need help with testing results

Thats the original info I sent you, the points are under the center cap you need to remove the 2 phillips screws and lift the cap off.

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

I pulled the flywheel and checked the points. The gap was set at .20. The insulator block looked good too. I grounded the coil to one of the bottom posts of the coil bracket. Still no spark when I tested using a battery powered drill to turn the flywheel. Is there a better place to ground the coil?? The wire doesn't allow you too many choices due to it's length. Thinking about taking coil to Autozone and have them test it. Got any additional thoughts??

 

[Laddies]

Re: 1971 4hp Merc no spark need help with testing results

Disconnect the wire that goes to the points and connect a jumper wire from the coil to ground this will tell if the points part of the system is grounded and anouther jumper from the orange stator wire to ground, this is a ground on system and the wire must be grounded to have spark, at that poin if the engine is turned over it should have spark.

 

[Laddies]

Re: 1971 4hp Merc no spark need help with testing results

Here's stator and coil specs from Mercury.

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

I just replaced the coil and that was not the problem. I'm going to try your test in a few minutes. The one issue I have is that I do not have the kill switch wire on this model. There is only the green wire from the stator. How should I do the test with just the 1 wire?? Also what side of the coil should the green stator wire go to. I'm assuming it should be the positive side.

 

[Laddies]

Re: 1971 4hp Merc no spark need help with testing results

Look on the test and on the picture and you will see it says that the orange is grounded on some 1 cyl. motors. Yours must be one of them, I checked and there are no wiring diagrams for the single cyl engines, so I can't send one.

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

There is only one stator wire(green) and the points wire. Does that mean in your directions to Disconnect the wire that goes to the points and connect a jumper wire from the coil to ground this will tell if the points part of the system is grounded. and disregard the part of connecting anouther jumper from the orange stator wire to ground, this is a ground on system and the wire must be grounded to have spark, at that poin if the engine is turned over it should have spark.

 

[Laddies]

Re: 1971 4hp Merc no spark need help with testing results

Yes, with the point wire disconnected and the coil terminal jumped to ground you should have spark, all the points do is act as a timer for the spark.

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

Still no spark. I disconnected the points wire and ran a jumper to ground. I turned the motor over with a portable drill and still nothing. What next??

 

[Outboard Mike]

Re: 1971 4hp Merc no spark need help with testing results

I repeated the stator test with the positive from my radio shack tester to the green stator and negative to ground with lead wires from stator disconnected. I get a 60 reading. When I reverse them I get no continuity. This is reverse of what it says in the Mercury Stator assembly and stator coil check test. I'm assumming this is due to the tester I'm using. Could this be it??

 

[Laddies]

Re: 1971 4hp Merc no spark need help with testing results

I believe so sounds like the leads are attached backwards.