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1987 6hp Evinrude missing

With a 2 cylinder outboard you probably wouldn't notice that quick of miss when idling. These motors run incredibly well on one cylinder, however with significantly reduced power.

It doesn't look like you are running on one cylinder so it must be an intermittent miss. This could be spark related or some other mechanical problems. The first thing I would do is an external spark test to confirm that your ignition is powerful enough to make the spark jump at least a 3/8" gap. If that is the case, then I would give a very close inspection of the secondary coils for any cracks in the insulation that might allow the current to leak out to ground. This usually happens when it is warm and at the higher voltage (WOT produces the highest voltage).

Take out the spark plugs and look to see if one is starting to foul and/or if you see the evidence of water. If you have another set of plugs, put them in and take her out again, just to rule the spark plugs out of the equation. A compression test would not hurt either.
 
I'd inspect the plugs for any abnormal appearance

Check sparks as suggested

I'd try new plugs. Correct type Champion QL77JC4 or QL86C gapped at 0.030".

Running fresh fuel at correct mix (50:1) with TCW3 oil ?
 
Run with a timing light on it.----When motor falters see if you have steady spark on top cylinder,----Repeat with bottom cylinder.
 
davidfogler said:
Anybody know what would cause this engine miss. It only does it under a load at high speed. Doesn't do it when idling, in geat at slow speeds, or reving high in neutral. Here's the video: http://www.youtube.com/watch?v=cWadF9R6Ii8&feature=plcp
Click to expand...

The engine isn't missing.... it's jumping out of and back into gear, hence the jumping effect on the transom one sees as this takes place.

(Jumping Out Of Gear - Manual Type)
(J. Reeves)

This pertains to lower units on all OMC manual shift outboard engines, or any OMC engine with lower units defined as a Shift Assist or a Hydro Electric Shift unit which incorporates a "Shifter Clutch Dog".

Within the lower unit, splined to the prop shaft is what is most often referred to as a clutch dog, hereafter simply called dog. The dog has at least two lobes protruding from it on both ends, facing both forward and reverse gear. The forward and reverse gears also have lobes built into them near their center area. When the engine is running, in neutral, the gears are spinning constantly via the driveshaft being connected directly to the powerhead crankshaft, but the propeller does not turn due to the fact that the dog is centered between the two gears, and the dog lobes are not touching either of the gear lobes.

When the unit is put into either gear, shift linkages force the dog (and its lobes of course) to engage the lobes of the gear. The lobes of the spinning gear grab the lobes of the dog, and since the dog is splined to the prop shaft, the propeller turns.

The lobes of the dog and gears are precisely machined, most with right angled edges that could be installed in either direction, and some with angles slightly varied that must be installed in one direction only (one end only must face the propeller). Dogs that can be installed in one direction only, if reversed, even if the dog and both gears were new.... would jump out of gear almost immediately. Keep in mind that the lobes are precisely machined with sharp angles!

Due to improper adjustment or worn shift linkages, but usually due to improper slow shifting, those precisely machined sharp edges of the lobes become slightly rounded. Now, with those lobes rounded, as the rpms increase, the pressure of the gear lobes upon the dog lobes increases to a point whereas they are forced apart (jumping out of gear), and due (usually) to the shift cable keeping tension on the engines shift linkages..... the unit is forced back into gear giving one the sensation that the engine has hit something, and the cycle continues.

Some boaters with manual shift engines have the mistaken belief that shifting slowly is taking it easy on all of the shifting components..... Wrong! Shifting slowly allows those precisely machined sharp edges of the dog and gears to click, clank, bang, slam against each other many times before they are finally forced into alignment with each other..... and this is what rounds those edges off! The proper way to shift is to snap the unit into gear as quickly as possible.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
joereeves said:
The engine isn't missing.... it's jumping out of and back into gear, hence the jumping effect on the transom one sees as this takes place.

(Jumping Out Of Gear - Manual Type)
(J. Reeves)

This pertains to lower units on all OMC manual shift outboard engines, or any OMC engine with lower units defined as a Shift Assist or a Hydro Electric Shift unit which incorporates a "Shifter Clutch Dog".

Within the lower unit, splined to the prop shaft is what is most often referred to as a clutch dog, hereafter simply called dog. The dog has at least two lobes protruding from it on both ends, facing both forward and reverse gear. The forward and reverse gears also have lobes built into them near their center area. When the engine is running, in neutral, the gears are spinning constantly via the driveshaft being connected directly to the powerhead crankshaft, but the propeller does not turn due to the fact that the dog is centered between the two gears, and the dog lobes are not touching either of the gear lobes.

When the unit is put into either gear, shift linkages force the dog (and its lobes of course) to engage the lobes of the gear. The lobes of the spinning gear grab the lobes of the dog, and since the dog is splined to the prop shaft, the propeller turns.

The lobes of the dog and gears are precisely machined, most with right angled edges that could be installed in either direction, and some with angles slightly varied that must be installed in one direction only (one end only must face the propeller). Dogs that can be installed in one direction only, if reversed, even if the dog and both gears were new.... would jump out of gear almost immediately. Keep in mind that the lobes are precisely machined with sharp angles!

Due to improper adjustment or worn shift linkages, but usually due to improper slow shifting, those precisely machined sharp edges of the lobes become slightly rounded. Now, with those lobes rounded, as the rpms increase, the pressure of the gear lobes upon the dog lobes increases to a point whereas they are forced apart (jumping out of gear), and due (usually) to the shift cable keeping tension on the engines shift linkages..... the unit is forced back into gear giving one the sensation that the engine has hit something, and the cycle continues.

Some boaters with manual shift engines have the mistaken belief that shifting slowly is taking it easy on all of the shifting components..... Wrong! Shifting slowly allows those precisely machined sharp edges of the dog and gears to click, clank, bang, slam against each other many times before they are finally forced into alignment with each other..... and this is what rounds those edges off! The proper way to shift is to snap the unit into gear as quickly as possible.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
Click to expand...

That makes perfect sense, because it didn't feel like an engine problem. It felt more like a gear problem. So what do I do to fix it?
 
The gearcase requires dismantling so that the shifter dog and forward gear etc can be inspected in order to determine what needs replacing. Also the shift linkage should be checked for play and/or proper adjustment.

Do not attempt this yourself unless you have a proper service manual amd are mechanically inclined.
 
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