1973 evinrude 18hp misfire like symptoms

[B.johnson1993]

[No message]

 

[F_R]

That motor definitely has an ignition problem. First things first, check the spark plugs. Better yet, try some new ones. If that isn't it, you will have to pull the flywheel and check the coils, points & condensers. And spark plug wires.

You will need a puller to get the flywheel off, and when you put it back on, make sure the tapers are shiny clean and dry and you MUST use a torque wrench to tighten the nut to 40-45 foot pounds.

 

[B.johnson1993]

When I bought the motor in April i checked the spark plugs and one of them was loose, turns out who ever did the plugs last over tightened one of them and pulled the threads out, I put a heli coil in it for short term until I get a replacement head, I notice there's oily residue coming out of that heli coil, would something like this cause that? I'll look into the ignition closer though

 

[hardwater fisherman]

Is there is leakage when the plug is in tight? Or do you see the oil when you take the plug out? If it is leaking around the plug then probably not too good. I think that model has external coils and if anything like my 40 hp with that ignition, the plugs may be fouled as F_R suggested. If it is not the plugs or plug wires then I would suggest to pull the flywheel and clean and gap the points. Or replace if in bad shape. The manual says to replace if pitted but I lightly file and sand them. I then CLEAN them and gap at.020.

 

[F_R]

Oh yeah, that's right. 1973 had that wonderful Lo-Tension magneto with external coils. But the points & condensers are still under the flywheel. Check them.

The leaking plug will make a mess and if bad enough could affect the idle, but it isn't causing that miss. Did you pull the head to do the heli-coil? Did you use a new gasket? Water leakage into a cylinder can cause a miss and also can totally destroy the engine.

 

[B.johnson1993]

No I didn't pull the head to do the heli coil,it was the cylinder that was accessible. And yeah the plugs are tight but slight oil leakage. If there was water leakage into a cylinder wouldn't I see it? Or would it be leaking internally

 

[oldboat1]

Replacement head is a good idea, but helicoils can work. I've done a couple -- recall one wanted to run back out when I removed the plug. Think that one just needed to be fixed back in place.

It might be worth trying to fix the current helicoil. After pulling the head cover, wouldn't it work to insert an old plug from the inside, then try to back out the helicoil? Or maybe that idea for reversing threading is just dumb....

Anyway, that head cover or another one, will want to resurface it before reinstalling. If it's warped a bit, you won't get a solid seal -- could give you operating problems. Think I would at least try resurfacing, using the existing gasket if its in decent shape. To resurface, move the mating surface of the head cover over a piece of wet/dry sandpaper (maybe 400 grit) on a hard surface. Some use a piece of glass. I use the top of my table saw. Use a figure 8 motion until all sufaces are equally shiny.

Clean up the cylinder with a shop rag and some 2-cycle oil -- look for any leavings from the last repair.

 

[F_R]

No I didn't pull the head to do the heli coil,it was the cylinder that was accessible. And yeah the plugs are tight but slight oil leakage. If there was water leakage into a cylinder wouldn't I see it? Or would it be leaking internally

It's a non-issue, since you didn't pull the head. But to clear up the question, gasket/water leakage into a cylinder would be internal and you would not see it.

The oil leakage around the plug won't affect the way it runs, but can make a mess. Your choice, what to do about it--if anything. A new plug with a fresh plug gasket might even seal it if it isn't too far out of alignment.

 

[racerone]

Run with a timing light and observe the light.----Might be able to determine which cylinder is missing.

 

[B.johnson1993]

Alright, replaced the points, I started it up in a barrel and it runs, haven't had it out on a lake yet, but now the throttle feels like there's a slight kink or notch in it that I don't remember being there before. Every time I take my hand off the throttle it turns itself to the stop position and dies out, did I not get something back together right?

 

[oldboat1]

Coils might not be mounted quite flush. Might also check to be sure coil/condenser/points wires aren't rubbing on the flywheel (need to tuck them in).

[edit. guess that would be just the driver coil....]

 

[B.johnson1993]

The coil driver was rubbing against the flywheel, I sanded the magnets smooth again and adjusted the coil driver in a little sonit isn't hitting, is there a spec for how far the coil driver should be away from the flywheel?

 

[oldboat1]

(I don't have a spec.)

Like under flywheel ignition coils, set the driver coil laminations perfectly flush with the throttle plate mounting posts. If all you did was clean up the magnets, that should give you the correct air gap.