75 HP Mariner Ignition Problem (This is a tough one)

[schuh]

My 87 Mariner has me stumped. It ran perfectly until 3 years ago when the boat it was on rotted out. It was

then stored outside on a stand under cover.

Mounted it on a new boat 2 weeks ago and it wouldn't start. I knew the stator and trigger coil windings were

iffy, wires beginning to corode where they entered the coils (Mariners do this). Checked the coil resistances

and the stator was bad. Bought a new CDI stator. Still wouldn't start.

Called CDI and they said the power pack can go bad just sitting, so I replaced that. Motor started and idled

great! Hallelujah!

Put the boat in at the local ramp for a short cruise, started and idled great. First 200 yards at idle no

problems, but when I tried at add a little throttle it sputtered. Adding choke helped some but finally it died

and would not restart. Time to call my buddy for a rescue.

Got the boat back home and it would not start. Since it ran slightly better for a while with the choke I

assumed gas problems. Changed the filter and added a little gas in the carb throats. Absolutely would not

start. Backfired twice through the exhaust, and once through the carb, but never fired up. I've never had any

motor that wouldn't run for a few seconds with gas sprayed in the carbs if it was a fuel problem, so I'm sure

its not fuel. Compression is fine.

Pulled the flywheel to check for a sheared key ... but no all is fine there. Checked the resistance on the

trigger coil and got 0 ohms on all three windings. Aha! The trigger coil finally pooped out. Bought a new CDI

trigger coil and installed ....... NOTHING!

As a last resort I made and drilled a strip of aluminum that I could screw all three plugs into and watch them

while I cranked the motor. Crank for 5 seconds - no sparks at all. Crank another 5 seconds, maybe one weak

spark and one fat one (should have been 30 or 40 sparks). Crank another 5 seconds, no sparks. Very

intermittant.

I'm usually a fair hand at diagnosing but this one has me stumped !!

Can anyone offer some suggestions? I'm sure it's electrical not gas, but all the electric componants are new

except the coils and they check out good (resistance). Besides if one or even two coils were bad it would still

kick over a little.

Help !!!

 

[racerone]

Take the starter apart for inspection.-----Load test the battery.--Slow cranking means a " no spark " condition.

 

[schuh]

There is no slow cranking. Battery is new and motor cranks very fast with starter.

 

[schematic]

if you have verified a no-spark condition, just go through the trouble-shooting steps on "CDIs" website.

Have you tried disconnecting the kill wire from the pack to see if spark returns?

 

[sam am I]

schematic makes a good point, the kill wire could be floating around the engine or hull somewhere with bared/crack insulation and intermittently shorting to or near ground shutting down the spark. Pull it at the power pack and re-test.

Other than that, the basics are (as far as Ignition) The stator has dedicated winding's (two on yours I think) that charge up the capacitors in the switch box that get dumped on the primary's of the plug coils to fire the plugs. The trigger winding's are the totally separate winding's that pick up the inside flywheel hub magnetic pulses and dictate/signals to the switch box when to dump a specific cap's charge on a specific coils primary which in-turns fires the appropriate plug (secondary)........Sounds to me like little or no charge is getting on those caps still/again. Maybe recheck the wiring harness's path/s from the stator to the boxes as well.

 

[Faztbullet]

There is only 1 capacitor in switchbox....

 

[schuh]

Thanks guys for all the suggestions. I didn't know CDI had a troubleshooting guide on their website - I will definitely check it out.

The kill wire was a good thought, but I already completely disconnected it and the symptoms remain the same.

Both the stator and the trigger coils are new from CDI. I will go out now and recheck the resistances just to make sure they did not break down after I installed them.

The switchbox (power pack) is new also but NOT by the CDI company. Right now I'm wondering if it worked on arrival and went dead shortly after. As I said the motor ran fine for a total of about 5 minutes (2 in the driveway and 3 on the water). Maybe it was inferior quality and just died. I will report back when I know more!

Thanks again.

 

[schuh]

THE SAGA CONTINUES

Went back and checked all my work. Both the stator coil and the trigger coil are new and all resistances match the specs exactly. Tried another switchbox that was taken off an older running Merc 65HP 3 Cyl and still nothing ... not even a single cylinder firing even with the black/yellow kill wire disconnected from the switchbox.

Is there any possibility that I have bad/broken reed valves ??. Would bad/broken reed valves keep the motor from firing at all ???

 

[racerone]

????---Thinking that you have a reed valve problem here is " grasping at straws "---The reed valves have to do with compression in the 3 or 4 seperate crankcases.

 

[sam am I]

If you have no spark "3 Cyl and still nothing ... not even a single cylinder firing" you said in a earlier post you had essentially have no spark, thinking ya just start with basics and work up.....Gotta have fuel, air and a ignition source to make fire

Start at page 66, "NO SPARK ON ANY CYLINDER:" Esp. check out how to manually bench test the switch box to fire a plug, pg 68.
Some good info in there

http://www.cdielectronics.com/wp-con...th-Edition.pdf

 

[schuh]

Will check everything on pg 68 CDI troubleshooting manual, Just for grins I found another switchbox in my junkpile and bolted it up. Still nothing. Thats 3 switchboxes I've tried and one of them brand new. Will report back when I complete pg 68.

 

[schuh]

SUCCESS !!!!! For posterity .... here is the solution to this problem.

I tried switching trigger coil leads and and spark coil leads. i could occasionally get sparks but they were very intermittent. Sometimes # 2 would fire strongly (only) and the next try #1 would fire strongly and 2 and 3 would fire intermittently. Some tests - none would fire. There was no consistency.

Since the stator, trigger and switchbox were all new I tested the coils for resistance - all of them matched the published specs almost exactly.

As a last resort i thought i would check the sparkplug wires. It was nearly impossible to pull them out of the coils and when i did only the wire came out leaving the small metal endpiece behind stuck in the coil. Additionally both the end of the wires (that were in the coils) and the socket on the coil that you insert the plugwire into were covered with a greenish goo.

I pulled all 3 coils off the engine, dug out the metal clips, cleaned the sockets, endclips, and wires and reassembled.

The motor started immediately and runs just fine. Apparently the green goo was insulating the plug wires from the coil secondary's. The slightest movement of the plugwires would make some connect better and others worse making the problem intermittent and sometimes produce no spark at all.

I have NO idea what made the green goo. Dielectric grease gone bad ???? I have never seen anything quite like it.