1974 Mercury 115 hp Outboard has no spark

[amazinthing]

I got this motor. I have installed new plugs (OEM) that the motor called for... It has great compression and turns over fine. how can i check to see if it is getting spark to the plugs? It just turns over but doesnt even attempt to start... It is part of my project bass boat. any help would be appreciated. I did read the post on the FAQ's about it... I just need an idiots walk through on this... when I primed the ball Gas did shoot out of my carbs...

 

[turbinedoctor]

Re: 1974 Mercury 115 hp Outboard

Re: 1974 Mercury 115 hp Outboard

There are two ways that come to mind quickly. 1) remove a plug, connect plug wire to it and ground the threaded end to the engine ground and crank the engine over to see if it sparks across the gap. 2) if you have a timing light you can hook it up to a spark plug or wire and see if it flashes while cranking the engine.


Durwood

 

[Chris1956]

Re: 1974 Mercury 115 hp Outboard

Re: 1974 Mercury 115 hp Outboard

If gas shot out of the carbs, the inlet needles or seats or floats are bad. You need to replace thme and clean up the carbs. New gaskets, new needles and seats and perhaps new floats. Those motors need to have the daylights choked out of them to cold start.

If it were me, I would do the spark test, and if you have spark, then work on the carbs. You might post back the results.

 

[amazinthing]

Re: 1974 Mercury 115 hp Outboard

Re: 1974 Mercury 115 hp Outboard

okay... i took a electricity light, one that light up when there is power to something... I put it inside the plug wire and attached the other end to the spark plug... I did not have any power whatsoever. I then opened the distributor cap and noticed the part in it with a spring and like a rough thin circular rock on some sort was cracked all to hell... Could that be a problem? what is that part called as I will probably need to get a new one

 

[amazinthing]

Re: 1974 Mercury 115 hp Outboard has no spark

bump for a response

 

[turbinedoctor]

Re: 1974 Mercury 115 hp Outboard has no spark

With out seeing the part you are talking about I would guess it is the rotor button. Does it sit on top of the shaft that turns when cranking the engine over?

 

[frwhlr38]

Re: 1974 Mercury 115 hp Outboard has no spark

ok after reading your posts it sounds to me like ya needs to replace the cap rotor the rotor is the thing with the spring as you dicribe you may also look into new plug wires also change points and condencer just my 2 cents BILL

 

[Chris1956]

Re: 1974 Mercury 115 hp Outboard has no spark

Bill, That motor does not have points and condersers.

Inside the distributor cap there is a carbon electrode on a spring. That seats in the center of the cap and allows high voltage to flow to the rotor. if yours is damabed, a replacemnt is <$5.

BTW the rotor is non-removeable. if you break it you must buy the shaft and rotor ($200+), and disassemble the distributor.

The proper way to spark test it is to either put a timing light on each plug wire and crank the motor and see if you have spark on all six. Since that is a distributor motor, if you have spark on one plug, you will most likely have it on all. The other choice is to remove the plugs from the motor, replace them in the plug wires, ground them to the block and crank the motor and observe the spark.

 

[amazinthing]

Re: 1974 Mercury 115 hp Outboard has no spark

I ordered the part to the distributor cap. It was 5.73 shipped what other parts could go wrong to not get spark to the plugs?

 

[amazinthing]

Re: 1974 Mercury 115 hp Outboard has no spark

TTT bump

 

[achris]

Re: 1974 Mercury 115 hp Outboard has no spark

Maybe a dead switchbox.... By the sound of your electrical knowledge, take it to a Merc shop....

Don't worry about the petrol shooting out the carb. If you over prime those engines, they do that.

Chris........

 

[amazinthing]

Re: 1974 Mercury 115 hp Outboard has no spark

okay... I can remove the distributor cap and hear, see, and even felt spark, but I cant see it get to the plugs... I got the new carbon electrode and put it in... now i see the spark, but cant get it to the plugs... any help would be appreciated

 

[amazinthing]

Re: 1974 Mercury 115 hp Outboard has no spark

looking for any ideas bump

 

[Chris1956]

Re: 1974 Mercury 115 hp Outboard has no spark

The spark travels from the ignition coil to the distributor, theu the carbon electrode, thru the rotor, and the the plug wires, via the cap electrodes. The wire from the coil to the distributor and the wires from the distributor cap to the spark plugs can arc to ground. Do you hear or see that? Is the rotor in good shape?

Tell us exactly how far the spark travels, before you lose it. Hold the distributor end of the coil wire (in unscrews from the distributor cap) 1/4 from the block and crank her. It should arc to ground. Repeat with a plug pulled from the motor and grounded. It should jump the gapless plug.

 

[Spimmmbler]

Re: 1974 Mercury 115 hp Outboard has no spark

Because i have done this myself. Make sure you battery cables are hooked up to the battery correctly. Having them backwards will not only cause you to have no spark but may cause damage. I hope you figure things out.

 

[cbell11]

Re: 1974 Mercury 115 hp Outboard has no spark

Not sure if you ever got your issue resolved but although this is an older thread, I was reading through it last night when trying to troubleshoot my issue and wanted to post my results incase anyone else makes the same stupid mistake I did.

Not sure if the Mercury's are the same way but the Mallory dist/cap that came on my 73 chrysler had 6 holes. on my 3 cyl 70 hp I struggled with changing points, coil, distributor, plug wires etc. fighting the no spark at the plug issue until I realized the spark plug wires were in the wrong three holes in the cap.. I had them stuck in the ones with the grounding strap.

 

[achris]

Re: 1974 Mercury 115 hp Outboard has no spark

Merc caps are different. They don't have points etc, that need changing and the spark plug leads are screwed into the cap.... Very difficult to remove accidentally and put back in the wrong place...