18hp Evinrude Odd Ignition Problem

[GDFL]

I have a 1967 Evinrude 18hp. It has been running really well lately until Saturday. It started dropping out on one cylinder. At idle or fast idle, it would run on one cyl and you could hear the other cyl fire ever now and then. When running in gear out in the water, it would occassionally get the boat planed off, but then drop the cyl after a few seconds. Here's what I know:
It does not have water in the fuel
It is not starving for fuel
I replaced the plug wires yesterday and have the same results
The ignition plate is not loose (stays tight)
New sparkplugs didn't help

I wanted to get some help before I bought new coils and condensers and such. Does anyone have any ideas to check? This is such a simple motor. I'm really frustrated that I can't figure it out.
Thanks,
Garrett

 

[CATransplant]

Re: 18hp Evinrude Odd Ignition Problem

It may well be that you didn't get one of those plug wires fully inserted into the coil. I'm assuming you used wires with real stranded copper inside. The intermittent nature of the problem points to something like that.

However, you could still have bad coils, dirty or maladjusted points, or even a bad condenser in there.

But, if it ran OK until you installed the new plug wires, that's where I'd look.

 

[tx1961whaler]

Re: 18hp Evinrude Odd Ignition Problem

The first thing I would try is cleaning up (emery cloth) and re-gapping the points. If that doesn't do it, then I just bite the bullet and spend about 55 bucks and get new coils, points and condensers. Once you do that, you'll have a whole new ignition system that you won't have to look at again for many years.

 

[GDFL]

Re: 18hp Evinrude Odd Ignition Problem

It may well be that you didn't get one of those plug wires fully inserted into the coil. I'm assuming you used wires with real stranded copper inside. The intermittent nature of the problem points to something like that.

However, you could still have bad coils, dirty or maladjusted points, or even a bad condenser in there.

But, if it ran OK until you installed the new plug wires, that's where I'd look.

It started running bad before I replaced the plug wires. I was trying to fix the problem. One of the metal inserts that goes on the plug was rusty and I was hoping that was the problem. The new wires (yes, they're stranded) was an attempt to fix it and it didn't work. I'll try cleaning and re-gapping the points next before replacing everything. I haven't checked compression yet. That wouldnt' be a compression issue would it?

 

[CATransplant]

Re: 18hp Evinrude Odd Ignition Problem

Well, low compression in a cylinder can cause it to misfire, certainly. For me, I consider a compression test a must whenever I have the plugs out of the engine. It just takes a few minutes.

However, from your description, it sounds like an ignition problem. If it were my outboard, of that age, and I was planning to keep it, I'd probably replace the entire ignition system and be done with it. Coils, points, condensers, and wires. But, cleaning and resetting the points is a good way to find out if you need to do that. The cam followers or rub blocks wear and that makes the point gap less than it should be. At some point, that can certainly cause a misfire, as can dirty points.

Still, since you have to pull the flywheel (a job I don't enjoy), you might consider just replacing it all. You shouldn't have to do it again within the next 25 or 30 years. If the coils are originals, I'd certainly do it. If they've obviously been replaced, probably I would just do the points, condensers and wires.

I guess it depends on how willing you are to pull and replace the flywheel multiple times.

 

[F_R]

Re: 18hp Evinrude Odd Ignition Problem

Speaking of the flywheel, it is absolutely necessary that you use a torque wrench and tighten the nut to 40-45 FT/LBS. Don't think you can guess at it. Many a motor has been destroyed that way.

Oh, and the shaft and flywheel tapers must be clean and dry.