Tuning Up - 1975 Johnson Sea-Horse 9.9HP

[beverly]

The motor is a 1975 Johnson Seahorse 9.9HP.
I did a tune up on the points and spark plugs, point contacts and carburetor alignment.

Under the flywheel looks like this
Coil packs attached on the side of the engine.

I wanna talk about the coils and sparks that zaps.

So far the spark plugs have been replace some years ago but they both work.
The one coil works very and newer looking new as even I remove it from the spark plug (top cylinder) I get zapped which results in the engine dies.

OK so it is the bottom cylinder with a problem.

As I remove the spark plug wire from the plug nothing happens in performance but as I start getting close to hook it back up to the plug the older coil pack starts sending sparks to the spark plug and the engine smooths out but as I put the wire fully on the plug it idles rougher and starts missing. If I bring the wire back to the sweet spot where its sending the sparks over to the plug it works well but it starts missing when it is too far apart or completely on.

I can touch and hold that wire all day and not get zapped but when I remove the other one I get zapped.

Week coil pack? Bad ground?

So why does the lower cylinder work when there is a gap between the spark wire and spark plug but doesn't when it is completely connected to the plug?

 

[LureheadEd]

Re: Tuned Up - Coils Pack New vs Old

Re: Tuned Up - Coils Pack New vs Old

First things first, try swapping plug wires, then the plugs, see if it changes to the other cylinder...

 

[beverly]

Re: Tuned Up - Coils Pack New vs Old

Re: Tuned Up - Coils Pack New vs Old

I did what LureheadEd said and started swapping.

1. Swapped the coil pack around and there was a change which kept to the one side of the wires (Light blue) [Blue with the line was the other wire]

So I followed suit.

I swapped condenser around with no effect
I swapped (well turned since it was one unit with two wires coming off) the stator with no effect

So it's either the wire (light blue) or the breaker or maybe ground

I don't see anything wrong with the wire

 

[beverly]

Re: Tuned Up - Coils Pack New vs Old

Re: Tuned Up - Coils Pack New vs Old

Things I've done


The breakers are good, clean and function properly. Set gap to .02
Check the ground wire(s) and cleaned
Checked the three wires (Ground; Right and Left coil wire) leading in to the amature plate and two checked out bad when I moved them around.

But it was still missing and wasn't idling properly.

I read up on the forum about using a different spark plug type BK7S made by NGK as the campions would foul up in a few days. This fixed the missing on one cylinder but now it was coughing now and then as it warmed up. At least the 9.9 was able to idle properly with a few coughs now and then but would cough a bit now with more rpms.

I tested the two coils on the side of the engine (one old and one new) with an ohms meter.
The newer one is tested
13.47k ohms (Prime wire to spark plug wire)
13.47k ohms (Spark plug wire to ground wire)
1.6 ohms (Prime wire to ground)

The older one is testing
11.56k ohms (Prime wire to spark plug wire)
11.56k ohms (Spark plug wire to ground wire)
1.4 ohms (Prime wire to ground)

Compared to a brand new one
13.25k ohms (Prime wire to spark plug wire)
13.25k ohms (Spark plug wire to ground wire)
0.6 ohms (Prime wire to ground)

Prime wire is solid blue in color and had a blue end tip connector except the old one which is black

The engine is a 1975 Johnson Sea-Horse 9.9HP





Every post that I saw had a 4000 to 8000 ohms testing and nothing about a 13000 ohms testing

 

[jim j geezer]

Re: Tuned Up - Coils Pack New vs Old

Re: Tuned Up - Coils Pack New vs Old

I'd say your meter and the lab's meter are somewhat different, accuracywise.

1. You've got pretty close matches.
2. Both coils fire their respective plugs - albeit one with an unplanned air gap. <--That's spooky!

I'd check (read: replace) the plug wire ends where they attach to the plugs.

Has the engine ever been dunked? I ask because if water + residue managed to find its way into coil housing where the plug wire emerges, then you might have a trace route to ground.

 

[beverly]

Re: Tuned Up - Coils Pack New vs Old

Re: Tuned Up - Coils Pack New vs Old

I'd say your meter and the lab's meter are somewhat different, accuracywise.

1. You've got pretty close matches.
2. Both coils fire their respective plugs - albeit one with an unplanned air gap. <--That's spooky!

I'd check (read: replace) the plug wire ends where they attach to the plugs.

Has the engine ever been dunked? I ask because if water + residue managed to find its way into coil housing where the plug wire emerges, then you might have a trace route to ground.

The measurements where compared to a $5 digital meter vs the Fluke 87 I use as a daily


I fixed that spark problem for coil 1 by replacing the amateur plate wires leads (coil 1, coil 2, ground). Apparently the one wire was faulty but then so was the other wire for coil 2. I didn't know about the ground wire being faulty but I replaced it anyways.

coil 1 is the old coil (guessing original)
coil 2 was replaced not long ago (last year to few years ago)

I don't know if the engine has ever been dunked before before me




Things to to.

I still haven't tested if coil 1 will zap me by holding the wire after replacing the amateur plate leads let alone if it will jump a 3/8 gap as I don't have a tester..

I already cleaned every contact except the push button to STOP the engine let alone de-grease the engine.

 

[jim j geezer]

Re: Tuned Up - Coils Pack New vs Old

Re: Tuned Up - Coils Pack New vs Old

Commercial spark tester:
http://www.autozone.com/autozone/ac...on-spark-tester/_/N-255s?itemIdentifier=10257