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cbach1981

New member
Hi all, I have finally decided to join the forums after using it to diagnose and fix Motors in the past. Now I'm at a standstill.

I have a 1987 Evinrude 40 horsepower vro engine, model number E40ELCUD. I was told this boat sat for 8 years, and the old dude that owned it had passed away and his family did not want it. I purchased it at a great deal, took it home and it fired right up.

When putting along at low speeds, the overtemp alarm came on. I decided to just go ahead and replace the impeller and the thermostat. I also rebuilt and cleaned both carburetors and change the spark plugs while I was at .

The issue I'm having is that the over temp alarm still goes off. I have checked the water jacket cover with a temperature gun, and the lower cylinder is much cooler than the upper cylinder. This can be as much as 30 degrees difference. I pulled the spark plugs, and the top one has a nice tan color. The bottom one still looks brand new, as if it just came out of the box. I have tried two different brand new spark plugs in that cylinder no change.

I re-cleaned the carburetors just to be sure that that was not my issue. If I pull the spark plug wire from the top cylinder, the motor will die. If I pull the plug from the bottom cylinder the motor dies down, but still runs. It seems to me that I am not getting fuel to the bottom cylinder, or at least not as much as I should be. Compression check with the engine warm and throttle wide open chose 125 psi in the top and 122 PSI in the bottom.

On this motor, one of the previous owners has done the vro delete. I am running a standard fuel pump on it now and pre mixing my own gas and oil. My question is with the carburetors at the front of the engine and the combustion chamber at the back, how is the fuel mixture getting into the cylinders? I would like to rule out a plugged Passage if I can do so fairly easily. Any other guesses or tips would be appreciated.

Thanks in advance,
Chris
 
It is a 2 stroke engine.-----Fuel / air / oil are first pulled into the crankcase.----Compressed and tranferred to the cylinder via ports..-----The brand new looking sparkplug indicates that there may be no spark.
 
I did pull the spark plugs and had my wife crank the engine well I checked them for spark. Both had a nice bright blue Spark. Is it possible that I have spark outside of the engine, but lose the spark once I install the plug? I do not have one of the Gap testers yet oh, so I have no idea if the spark will jump a 7/16 inch Gap. Again, I have installed two new spark plugs on the cylinder and both of them come out still looking new, although there is a little bit of wetness them it is nowhere near what I would expect if it was not firing at all. Thanks again for the help
 
I also tried swapping the plug wires to see if it followed, it did not. I swapped coils, still did not follow. So I think I have ruled out coils, wires, and plugs. So maybe the power pack isn't putting out what the coil needs?
 
Everybody blames the mysterious power pack. If it is getting spark on both cylinders, that ain't it. Check compression. Motor may have serous internal damage.
 
Seems to me the bottom cylinder isn't getting fuel. Have you tried spraying gas directly through the bottom carburetor? Are the two carbs opening the same when you change throttle?
 
This is my thought as well. I plan to try spraying gas in the lower carb tomorrow, as I work nights. I also intend to snag the inspection camera from work and take a good look at the cylinder walls. The carbs do seem to be sync'd pretty well.
 
So, using the inspection camera the cylinder walls look good. Unfortunately it was too big to sneak into the intake port. Spraying gas in the bottom carburetor made the engine bog down a little bit, but did not help as far as getting fire on that cylinder. I am getting a spark gap tester today and we'll make sure that the spark will jump a 7/16 inch Gap. I also put brand new spark plug wires on, just to eliminate that. When I pull the bottom plug, it is not wet. Nothing like I would expect if the cylinder was not firing. I think this may be a fuel delivery issue, not getting fuel from the carburetor into this cylinder. Potential reed valve issue? Maybe it isn't opening. This thing did sit for 8 years, I suppose they could have stuck shut.
 
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Checked the Reed valves, all looks good there. Did the spark gap test, the bottom one was lucky if it would jump a quarter inch Gap,it had no chance at 7/16. So, going with the fact that I had already tried swapping the coils and it made no difference, what should I look at? What actually sends the electricity to the coil oh, and how can I test that it is sending the right amount?
 
1. A "charge coil" under the flywheel generates the electricity for both cylinders. So if it is making juice for one cylinder, it is making juice for the other one as well

2. From there, the electricity is fed to the power pack, rectified and stored in a capacitor until time to fire---again, same for both cylinders

3. A sensor also under the flywheel senses when it is time to fire and sends a voltage to the power pack, the voltage having positive polarity for one cylinder and a negative polarity for the other cylinder. Again, same sensor and wires for both cylinders. Polarity is determined by which end (north or south pole) of the magnet is passing by the sensor.

4. Here s the only place the two cylinders are different. There are two SCR's (electronic switches) in the power pack. One SCR is turned on by a negative voltage fromm the sensor and the other SCR is turned on by a positive voltage from the sensor. One SCR, if turned on, causes the capacitor to discharge through it's respective external coil. The other SCR, if turned on, causes the capacitor to discharge through the other external coil.

5. You tell me, can a SCR turn on only half way? I honestly don't know the answer to that one. In any case, if there is a problem with the SCR's, the only cure is replacement of the power pack.

6. There is no voodoo in electricity.
 
This is exactly what I was after, thanks! I am going to see if I can find a buddy with a compatible power pack to verify. And I know there is no voodoo. At work it is referred to as M.E.S. (Mysterious Electrical S**t) haha!
 
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