weak spark

[killertrance]

hi,i have an old archimedes penta 25 hp twin cylinder model engine,the problem is i have a weak sparl on the bottom plug,ive swopped plugs over no effect,tried swopping coil wires andthis improves it,so i know the coils are ok,top one goes weak,ive got the flywheel off and the points <2 sets of > seem pitted and old,culd these be my problem. or condensers,or maybe a bad feed wire???thanx in advance for any help,oh it used to run but after five minutes it wuld drop onto one cylinder for a while,now it wont start at all...

 

[steelespike]

Re: weak spark

Can't help you specifically with that motor but the systems are similar on most outboards.I would start by replacing the plug wires.Check the connections where they go in the coil.new wires need to be solid core
(wire centers)Clean up the fly wheel,armature and the points and set them to .020
at the highest point of the cam.Most likely any outboard condenser that can be adapted to it will work.
If it continues to fail as it runs you will need to replace the suspect coil.If there are any indications of external
cracks or corrosion the coils should be replaced anyway.
Years ago I took the coils off the armatures of one brand of motor and put them on the armature of another.
If you can't find parts perhaps you can try it.

 

[tmcalavy]

Re: weak spark

I'm with Spike on this one. Clean and regap the points and retest, then do the plug wires. Condensors rarely go bad. Also check all the connections for both coils, points, condensors.

 

[killertrance]

Re: weak spark

hi,thanks for replying guys,today i swopped the coils over from top to bottom and vice versa now my engine runs on both cylinders.....ive noticed a little spark coming from a bracket that connects to the underneath of the stator plate wen the engine is running tho, is this normal???ive put a new earth strap from engine to cowl on,didnt stop sparking tho.the stator plate is loose aswell,is this supposed to be a good fit,it just wobbles about slightly under the flywheel.thanx in advance regards,jeff

 

[tmcalavy]

Re: weak spark

Stray spark could be source of your weak spark at one of the cylinders after awhile. Try new solid core plug wires and try to figure out where that stray spark originates. You can recoat old toasty coils with liquid electricians tape and sometimes get a little more mileage out of them.