Mercury 9.8 hp weak spark

[jperrone]

I recently purchased a 1970 model 110 9.8 hp merc.<br />with a Thunderbolt ignition. It ran at first(poorly and no idle and started extremely hard).<br />A mechanic friend determined that the upper cylinder had an extremely weak spark. The engine ran the same with or without a plug wire. The stator contains a large capacitor and 6 coils. Points and wiring seem ok. We swapped the ignition coils and now both cylinders have a weak spark. Going down hill fast<br /><br />John

 

[Chinewalker]

Re: Mercury 9.8 hp weak spark

Hi John,<br /> I am guessing the armature, or "donut" is bad. The coils and points in those generally don't go bad with age. If you can find a used donut, you'll be doing okay. New ones are available, but they are EXPENSIVE. Last I priced them they were over $200.00 - a good chunk of the whole motor's worth. Before you replac the donut, try replacing the points. They're not cheap either, but they can sometimes make a difference on those "maker" point ignitions. The manual claims the points don't have to be replaced, but I've found they do get bad at times.<br /> Another option would be to retrofit your motor with an earlier style ignition with the coils under the flywheel. Not easy, but it can be done.<br />- Scott

 

[jperrone]

Re: Mercury 9.8 hp weak spark

Scott<br /> I know buying a new stator will set me back $325 new.... That exactly what the motor cost. I like your idea of retrofitting the motor. The donuts seem to be pretty scarce but I might be able to pick up the older style parts.<br />I think its time for a change of tactics.<br /><br />Thanks John

 

[S.T. Marine]

Re: Mercury 9.8 hp weak spark

John,<br /><br /> I have a complete parts motor. If you need any electronics e mail me thanks

 

[dmessy]

Re: Mercury 9.8 hp weak spark

Before going out a buying a stator assembly, start checking each component out throughly. Is the resistance the same on both coils? Are the plug wires and ends unbroken and free of corrosion(and the wiring from the pickup coils) Are the points gapped and timed correctly?... You know peice by piece, one step at a time. I highly doubt your stator is bad as they are bulletproof ,however...

 

[KIWI MERCMAN]

Re: Mercury 9.8 hp weak spark

John <br />That model has 2 white plastic insulating blocks that the points wire goes through at the bolt.<br />These crack and can be very hard to see the cracks.(shows up more like carbon tracks)<br />The voltage will track to ground from these, I would advise you to replace these anyway.<br />Have seen alot of guys change stators and the only problem was the blocks.<br /><br />Kiwi