b71 40 hp Evinrude No Spark

"I'm new to the boating se

"I'm new to the boating servicing world and at a loss. I own a 1971 Ski-twin Evinrude 40 HP motor. The boat was running, serviced and still running, sold, pickled, and sat for 7 years. I have cleaned the carb, flushed the fuel and checked the wiring but the motor will not start.

The motor turns over with sufficient speed (I assume) but no spark is generated, (actually very very weak spark on contact of plug wires to ground). I don't think my motor has a power pack which seems to be the cause of most people's problems. Also, the wiring schematic shows a vacuum/cutoff switch and safety switch inline with the ignition works so I tried bypassing them and the thing still doesn't spark.

I would suspect the coils or the little condenser next to the coils, because it's the only thing I haven't been able to eleminate/test. But at this juncture don't have a clue.

Please help, Thanks."

"Are you assuming that you hav

"Are you assuming that you have no spark because the engine doesn't run, or are you actually checking the spark? The spark plugs must be removed in order to check the spark properly.

Does the engine incorporate a instrument wiring harness whereas a ignition switch exists, or do you simply have a push button setup? Even if you have the ignition switch setup, is there still a kill switch button on the engine or elsewhere?

The spark at cranking speed should jump a 1/4" gap with a strong blue lightning like flame. Let me know what happens there.

You cannot use the spark plugs as a spark testing tool. You must have that 1/4" gap set up.

Spark Tester - Home Made
(J. Reeves)

A spark tester can be made with a piece of 1x4 or 1x6, drive a couple nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:


..........X1..........X2

.................X..(grd)

..........X3..........X4

Clean the points with either acetone or laquer thinner. Set the points, having the flywheel key aligned with the fiber rubbing portion of the points. Set them so that a .020 gauge passes thru but a .022 will not.

Spark plugs should be either Champion J4C or J6C plugs,m gapped at .030. The J6C is slightly hotter and may provided a better idle.

The condensers are part number 581419, available at any Evinrude/Johnson dealership.

Did you manually clean the fixed brass high speed jet which is located in the bottom center portion of the float chamber. If not, do so with a piece of single strand steel wire.
(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.

Note: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.

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.

Let us know what you find."

"Thanks Joe for the indepth re

"Thanks Joe for the indepth response. And putting up with the noob.

I checked for spark with a wire inside the plug wire (I'm positive of good connection) and held it 1/4" or closer to the plug's ground (or powerhead tried both) checking for spark. I read in an online guide that one should try grounding the other plug so I tried that too while checking for a spark.

Yes there is a wiring harness, key switch, etc, but no kill button at the engine.

I cleaned the gaps with acetone but have not checked the gap. I will borrow some feeler gages and verify that tomorrow afternoon.

Plug is correct type and I checked the gap earlier it's correct.

I do not really understand "Did you manually clean the fixed brass high speed jet which is located in the bottom center portion of the float chamber. If not, do so with a piece of single strand steel wire." but will get into that when I get back to work on it tomorrow afternoon.

I will see if building a more complicated spark tester tells me anything but I don't see why they would.

You telling me that condensers are available at any dealership the same as telling me to go ahead and replace?"

If you have cracking on the co

If you have cracking on the coils this could be your problem as well. Spark will jump from coils to ground under the flywheel. You may or may not still have weak spark at the plugs in this condition. If spark is good remove plugs and spray SMALL AMOUNT of starting fluid in cylinders replace the plugs and try to start. If engine fires move on to the fuel system.