how do I know (for sure) if a coil is not working (1989 9.9 two stroke)

[tfbrown1270]

I have had trouble periodically with this motor for the last few months but had not located a fault till today.
It will not start without advancing the throttle by hand (by pulling forward on the cam follower) and even then it runs poorly, missing as though on one cylinder.
Having noted that I removed the spark plug wires while running as above, and noted the engine stops when the bottom spark plug is disconnected but the top one makes no difference. I concluded that the top plug is not firing but don't know why.
I see no way to switch ignition coils to see if the problem follows the coil because the wires are not removable (or so it seems) from the coil.
Should I throw parts at it? Seems the coil is likely responsible.
Are the coils expensive? Do I replace the two together or just one?

 

[Wingedwheel]

Re: how do I know (for sure) if a coil is not working (1989 9.9 two stroke)

A coil is expensive enough. You can do a basic check with an ohmmeter. From ground across secondary(output) you should read some resistance, say 7-9 ohms I believe. Typically the problem in a coil is the secondary. If it shows open you found your problem.

 

[tfbrown1270]

Re: how do I know (for sure) if a coil is not working (1989 9.9 two stroke)

Thanks for the reply; I found that switching the coils revealed the problem stayed with the top cylinder not the coil.
As a result I concluded it might be the switch box.
I have no idea how to prove that though and the price is prohibitive ($340 taxes in locally) making throwing parts at it impossible.
Any ideas would be greatly appreciated!

 

[Wingedwheel]

Re: how do I know (for sure) if a coil is not working (1989 9.9 two stroke)

Its never cheap to repair a marine engine, aspecially if its electronics. Do you have an outboard salvage yard anywhere near you? Thats always an option. Or check craigslist for a parts motor.