'69 Evinrude 9.5 Losing A Cylinder

[Busy]

I have a 1969 Evinrude 9.5 that ran perfectly last year. Stored inside all winter, new gas. Took it out yesterday and idled it for awhile, idled fine. Getting up to speed it lost a cylinder. Bottom spark plug wasn't hot. Trolled and fished for a while with the motor off to let it sit. Took the gas line off and turned the motor over several times. The second cylinder fires only intermittantly and I only seem to lose it at WOT. Every time I open it up the second cylinder drops out and comes back on when I throttle it back down.

What would be the most likely cause of this? I would think if it was in the magneto or ignition related it would either fire or not, instead of being intermittant.

[Nitrofreak]

Most likely a plug, plug wire, or coil, under load the ignition system has to push current, if any one of those 3 have high resistance it will cause it not to spark, look for carbon tracking on the plug insolation, the plug wire, check at the tip of the plug and look at the electrode for wear.

I don't know how long it has been since a tune up was performed but it sounds as if it is due for one.

[Busy]

Will try plugs and plug caps and keep my fingers crossed. Don't want to take the flywheel off unless I have to. I didn't realize that a coil would work at low throttle but not at WOT. The intermittant dropping out had me pretty confused. Thanks for the fast reply! I really don't think the plug got fouled.

[Nitrofreak]

A magneto either works or it dont work in most cases, in some, I have seen them to be very weak, and in those cases the key has sheared and allowed the flywheel to move.

I am not saying the plug is fouled, although it may very well be, there could be a crack in the plug and you may not be able to physically see it, but if there is, voltage will take the path of least resistance and travel elsewhere, possibly grounding itself.

A coil will do the same thing, look for white areas around the coil, some is normal a lot is a good sign of leakage.

A plug wire/boot if routed close to the engine will be able to leak as well, allowing voltage to escape through the insolation and ground to the engine block, if the wire is damaged internally it will cause a backup in voltage and it too could cause a premature coil failure.

One other note: it may be a power pack as well, if equipt with one but the only way to know for sure is to take it to a good tech.

[Way2slow]

Most likely, you will need to remove the flywheel. I would install a new set of points and condinsor and both plug wires. Points should be set so a .020" feeler guage will slide through them on high cam and have a small drag but not open the points any when inserted. Coil should should be gaped at approx .008" with a brass feeler guage. Usually when plug wires go bad, they will idle and run at mid rpm fine but start breaking down under a load. It would probably pay you to do a compression check also. I think those run approx 135 pounds.

A linc and sinc should be done also and check the timing.

If all that fails, you might want to consider a new coil.

[Nice_Bass]

coil

[Busy]

Changed the plugs and went out yesterday. Ran great!! Thank you for the replies.

The old plugs probably only had 10 hours on them and looked fine from the outside, but the new ones seemed to do the trick.

[Nitrofreak]

Changed the plugs and went out yesterday. Ran great!! Thank you for the replies.

The old plugs probably only had 10 hours on them and looked fine from the outside, but the new ones seemed to do the trick.

Glad to hear it !!

Even though they look good does not mean they are good.

Good luck and be safe !!!