1977 70 hp johnson no spark help

My motor has devoloped a slig

My motor has devoloped a slight/ intermittant miss I replaced the spark plugs w/ autolite2634 the old plugs championL-77J4 were basically burned away (I think they were the originals) any way the intermittant miss persisted . Tonight on a picknic cruise with the wife running at 4300 RPM it just shut off dead. I pulled out the spark tester and all cyls dead. All these years w/no maintenance are catching up I guess. how do I go about testing the powerpack and related components or do I just start changing parts?

" You have 3 ignition coils ,

" You have 3 ignition coils , they do not all fail at the same time. 3 sensor coils and they do not fail at the same time. The likely suspect part is the cd box. "

" Freedomflyer,

If yo

" Freedomflyer,

If you look a post down or two you'll see my post pertaining to a 85 HP of the same year. The ignition systems are only slightly different, yours has 3 cylinders, mines got 4, the trouble-shooting is the same.

I believe your power pack has 12 posts, it's hidden by a faceplate in the back of the engine. Here's what my book is showing for that pack. So this will fit on one page let IC mean Iginition coil, CC mean charge coil, IS ignition switch, VAC vacant, SENS sensor.

7(VAC) 8(SENS 1) 9(SENS 2) 10(SENS 3) 11(SENS common) 12(Ground)

1(IC 1) 2(IC 2) 3(IC 3) 4(CC) 5(CC) 6(IS)

so, that's what your pack is going to look like. I'm not sure how it's oriented in relation to this though (it may be upside down).

The first thing to do, if none of the cylinders are sparking, is be sure that lead 6 is not grounded, when the key switch is on; that's the ignition lead, which kills the ignition when ground is applied.

Jon "