1976 35 HP Low Speed Issue

[Florida-Evinrude]

Hello Experts

I have a 1976 35 HP motor that I considered a diamond in the rough.
Compression is 140 PSI in each piston and hate to give up on it.
What I have done so far on the ignition, cooling system, and carburation:
- Flywheel, points, plugs, condensers, driver coil, ignition coils, new points, ignition wiring, armature plate delrin ring, new water pump, rebuilt carburetor, new fuel pump. Timing is pinpoint using a timing device according to factory repair manual instructions and great spark is produce. Fuel delivery to the carburetor is good with no air leaks.

The motor will start fine and idle until it warms up, then it will not operate under 1800 RPM. One piston seems to drop out, runs for a few seconds and stalls. It takes a few minutes to get stated again, but will only operate at 1800 RPM and above. At high speed it runs flawlessly up to 4800 RPM.

I have a notion of what needs to be done, but would like to get comments from the Forum.

[Joe Reeves]

Within your post, you state: What I have done so far on the ignition, cooling system, and carburation: Flywheel, points, plugs, condensers, driver coil, ignition coils, new points, ignition wiring, armature plate delrin ring,

What exactly does this mean... that you've replaced these parts, looked them over and reused them, what?

When the problem arises... is the compression still 140 psi on both cylinders?

With the spark plugs removed, use a spark tester whereas you can set the spark air gap to 3/8". The spark should jump that gap with a strong blue lightning like flame... a real SNAP! Does it? Note that the air gap is important!

[Florida-Evinrude]

1976 35 HP Low Speed Issue

All the components I mentioned are new OMC, except the flywheel which was used but very little.
I never rechecked the compression after experiencing this event.
A spark tester was used to gauge the strength of the spark.
I even measured the input voltage to the ignition coil to make sure they were the best they could be at an average of 20VAC.
I'll test the engine tomorrow and take a compression test after operating through that same issue & scenario.

[Florida-Evinrude]

1976 35 HP Low Speed Issue

Well, I removed the spark plugs and retested the ignition coils this morning and found the bottom (brand new) ignition coil was episodically not developing the spark it should, it was weak. I used the top power supply to see if that made a difference; it did not. Luckily, I had one of the original ignition coils and tested it with both the top and bottom power supplies and the spark was strong using the top and bottom power supply.
I re-installed the spark plugs and ran the motor for 20-30 minutes between idle and mid-range speed. It was much better, but something still not quite right at idle ... a bit rough and an occasion skip; mid-range speed is very good.
Compression is still a strong 140 PSI in each cylinder.

Now I'm beginning to think the top crankshaft seal is leaking; at low speed it seems to have more of an effect than higher speeds.
Also, I notice the area underneath the armature plate is very oily.

Your thoughts?

[Joe Reeves]

I've never encountered a top C/S seal to affect crankcase pressure to a point where it would affect the running of the engine... BUT... that area should NOT be oily as you mention. Oil is an enemy of ignition points and oil on point WILL definitely affect the engine's performance. I'd replace that seal.

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(Point Setting Of Magneto Models)
(J. Reeves)

Note that there are other ways to set points such as using a ohm meter or timing light... however, the following will result in a setting so close to being exact that one could not tell the difference.

Make sure that your feeler gauge is absolutely clean so as NOT to transfer oil/grease to the points.

Set the points as follows. Have the flywheel key aligned with the fiber rubbing portion of the ignition points. Adjust the gap so that a .020 gauge will p*** thru but a .022 will not. Should there be any question of the points being dirty (touching the contact with your finger would cause them to be dirty), clean them with a small brush and acetone or lacquer thinner.

NOTE 1: Should the operating cam have a small portion on it with the word "SET" imprinted, align this portion with the fiber rubbing portion instead of the flywheel key.

NOTE 2: Should the cam have the word TOP embossed on the top of it, that is a cam that could be installed upside down and this is simply telling you which side is up. It is not a position where one would set the points.

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:

joe_omc32 | eBay
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[Florida-Evinrude]

1976 35 HP Low Speed Issue

Thank you Mr. Reeves for your response.
I agree that the points are very sensitive to contamination. I'm just a hobbyist with outboard motors and lean to the vintage and antique models due to there simplicity and ease of problem solving to get them to run. I try and follow all the repair manuals directions, but there is always that one condition that confounds you that only experience and logic can solve. In this case it might me a compound problem between the ignition coil and the upper crankcase seal. Next I'll change that seal and report back.

What would be your opinion about the reeds?
How would they effect the operation of a motor at high and low speeds?
I've read that they rarely fail?

[Joe Reeves]

If a reed/leaf valve was cracked, broken, not centered properly... you would have fuel being blasted out the carburetor throat with every downward plunge of the related piston. Not a likely prospect in your case.

What spark plugs are you using in that engine? That powerhead design demands Champion UL81J plugs gaped at .030. Possibly hard to find... BUT... if you can find them, they'll make a world of difference if everything else is as it should be.

I also meant to include, and thought I did, but I don't see it here so I will enter it now (below):

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(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

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:

joe_omc32 | eBay
*********************

[Florida-Evinrude]

1976 35 HP Low Speed Issue

Hi Joe:

Sadly to say, after replacing the upper crankcase seal and testing at WOT, the symptoms returned of the motor misfiring and dying out when brought back to idle.. After removing the flywheel, I noticed the seal leaking and subsequently the fuel-mix getting into the points.
In addition, I notice after grabbing the crankshaft at its end during the examination had some very minor play in it.

Should there be any play at all?

Something tells me the upper bearing may be the issue. Also, I could not get the engine to idle unless the points were set at 0.018 for the upper & 0.012 for the lower pistons.

I am now evaluating if I should do an entire rebuild.
There are two choices I'm considering:
1. Rebuild this 1976 Evinrude 35 HP with 0.030 over pistons, bearings etc.
2. Rebuild a 1983 Evinrude (electronic ignition) with 0.030 over pistons, bearings etc. ...this motor has compression of 140lbs & 120lbs.

Your thoughts?

[Joe Reeves]

No, unfortunately there should be absolutely no play (sideways) at the top main bearing area.

Note that it has been my experience (many times) that a lower main bearing could be faulty and transmitting that play as a wobble to the upper main... hint here is to check all main bearings.

My thoughts?...... If you're capable of doing this job, with that kind of compression (140) on the 1976 model... I'd leave the cylinder head on, there would be no need to disconnect the rods from the crankshaft... Just be absolutely sure that the bearings are seated properly in/on their seating pins when re-installing, and if any doubt about the seating... disconnect the rods to get them out of the way.

Use (OMC Adhesive is now Bombardier 3M Product #847 and may be listed as Scotchgrip 847, part number 776964.) on the spaghetti seals.

The cost would be of course far less than that later model which you can always do later in life.

[Florida-Evinrude]

1983 Evinrude Rebuild

Greetings Gentlemen

See the attached photograph.
The pitting you see is on the top piston, the bottom piston was fine.
The head area for the top piston also showed pitting.
Is the pitting caused by pre-detonation problems of wrong spark plug?
This is a 1983 Evinrude 35HP ... I'm rebuilding it and plan on a 0.040 overbore with Wiseco forged pistons.